58 files changed, 264 insertions, 265 deletions

diff --git a/src/mailman/app/moderator.py b/src/mailman/app/moderator.py
index 78332b84a..9a65207a6 100644
--- a/src/mailman/app/moderator.py
+++ b/src/mailman/app/moderator.py
@@ -31,12 +31,11 @@ __all__ = [
     ]
 
 
+import six
 import time
 import logging
 
 from email.utils import formataddr, formatdate, getaddresses, make_msgid
-from zope.component import getUtility
-
 from mailman.app.membership import add_member, delete_member
 from mailman.app.notifications import send_admin_subscription_notice
 from mailman.config import config
@@ -51,6 +50,7 @@ from mailman.interfaces.messages import IMessageStore
 from mailman.interfaces.requests import IListRequests, RequestType
 from mailman.utilities.datetime import now
 from mailman.utilities.i18n import make
+from zope.component import getUtility
 
 
 NL = '\n'
@@ -86,8 +86,8 @@ def hold_message(mlist, msg, msgdata=None, reason=None):
     # Message-ID header.
     message_id = msg.get('message-id')
     if message_id is None:
-        msg['Message-ID'] = message_id = unicode(make_msgid())
-    assert isinstance(message_id, unicode), (
+        msg['Message-ID'] = message_id = make_msgid().decode('utf-8')
+    assert isinstance(message_id, six.text_type), (
         'Message-ID is not a unicode: %s' % message_id)
     getUtility(IMessageStore).add(msg)
     # Prepare the message metadata with some extra information needed only by
diff --git a/src/mailman/app/notifications.py b/src/mailman/app/notifications.py
index 1fa1fe01e..99cbf0d0e 100644
--- a/src/mailman/app/notifications.py
+++ b/src/mailman/app/notifications.py
@@ -31,9 +31,6 @@ import logging
 
 from email.utils import formataddr
 from lazr.config import as_boolean
-from urllib2 import URLError
-from zope.component import getUtility
-
 from mailman.config import config
 from mailman.core.i18n import _
 from mailman.email.message import OwnerNotification, UserNotification
@@ -41,6 +38,8 @@ from mailman.interfaces.member import DeliveryMode
 from mailman.interfaces.templates import ITemplateLoader
 from mailman.utilities.i18n import make
 from mailman.utilities.string import expand, wrap
+from six.moves.urllib_error import URLError
+from zope.component import getUtility
 
 
 log = logging.getLogger('mailman.error')
diff --git a/src/mailman/app/templates.py b/src/mailman/app/templates.py
index 742584b49..d0c278e3a 100644
--- a/src/mailman/app/templates.py
+++ b/src/mailman/app/templates.py
@@ -25,22 +25,22 @@ __all__ = [
     ]
 
 
-import urllib2
-
 from contextlib import closing
-from urllib import addinfourl
-from urlparse import urlparse
-from zope.component import getUtility
-from zope.interface import implementer
-
-from mailman.utilities.i18n import TemplateNotFoundError, find
 from mailman.interfaces.languages import ILanguageManager
 from mailman.interfaces.listmanager import IListManager
 from mailman.interfaces.templates import ITemplateLoader
+from mailman.utilities.i18n import TemplateNotFoundError, find
+from six.moves.urllib_error import URLError
+from six.moves.urllib_parse import urlparse
+from six.moves.urllib_request import (
+    BaseHandler, build_opener, install_opener, urlopen)
+from six.moves.urllib_response import addinfourl
+from zope.component import getUtility
+from zope.interface import implementer
 
 
 
-class MailmanHandler(urllib2.BaseHandler):
+class MailmanHandler(BaseHandler):
     # Handle internal mailman: URLs.
     def mailman_open(self, req):
         # Parse urls of the form:
@@ -57,7 +57,7 @@ class MailmanHandler(urllib2.BaseHandler):
         # path components are legal, filter them out.
         parts = filter(None, parsed.path.split('/'))
         if len(parts) == 0:
-            raise urllib2.URLError('No template specified')
+            raise URLError('No template specified')
         elif len(parts) == 1:
             template = parts[0]
         elif len(parts) == 2:
@@ -69,25 +69,25 @@ class MailmanHandler(urllib2.BaseHandler):
             language = getUtility(ILanguageManager).get(part0)
             mlist = getUtility(IListManager).get(part0)
             if language is None and mlist is None:
-                raise urllib2.URLError('Bad language or list name')
+                raise URLError('Bad language or list name')
             elif mlist is None:
                 code = language.code
         elif len(parts) == 3:
             fqdn_listname, code, template = parts
             mlist = getUtility(IListManager).get(fqdn_listname)
             if mlist is None:
-                raise urllib2.URLError('Missing list')
+                raise URLError('Missing list')
             language = getUtility(ILanguageManager).get(code)
             if language is None:
-                raise urllib2.URLError('No such language')
+                raise URLError('No such language')
             code = language.code
         else:
-            raise urllib2.URLError('No such file')
+            raise URLError('No such file')
         # Find the template, mutating any missing template exception.
         try:
             path, fp = find(template, mlist, code)
         except TemplateNotFoundError:
-            raise urllib2.URLError('No such file')
+            raise URLError('No such file')
         return addinfourl(fp, {}, original_url)
 
 
@@ -97,10 +97,10 @@ class TemplateLoader:
     """Loader of templates, with caching and support for mailman:// URIs."""
 
     def __init__(self):
-        opener = urllib2.build_opener(MailmanHandler())
-        urllib2.install_opener(opener)
+        opener = build_opener(MailmanHandler())
+        install_opener(opener)
 
     def get(self, uri):
         """See `ITemplateLoader`."""
-        with closing(urllib2.urlopen(uri)) as fp:
+        with closing(urlopen(uri)) as fp:
             return fp.read().decode('utf-8')
diff --git a/src/mailman/app/tests/test_templates.py b/src/mailman/app/tests/test_templates.py
index afde68647..40ec6d234 100644
--- a/src/mailman/app/tests/test_templates.py
+++ b/src/mailman/app/tests/test_templates.py
@@ -26,18 +26,18 @@ __all__ = [
 
 
 import os
+import six
 import shutil
-import urllib2
 import tempfile
 import unittest
 
-from zope.component import getUtility
-
 from mailman.app.lifecycle import create_list
 from mailman.config import config
 from mailman.interfaces.languages import ILanguageManager
 from mailman.interfaces.templates import ITemplateLoader
 from mailman.testing.layers import ConfigLayer
+from six.moves.urllib_error import URLError
+from zope.component import getUtility
 
 
 
@@ -98,32 +98,32 @@ class TestTemplateLoader(unittest.TestCase):
         self.assertEqual(content, 'Test content')
 
     def test_uri_not_found(self):
-        with self.assertRaises(urllib2.URLError) as cm:
+        with self.assertRaises(URLError) as cm:
             self._loader.get('mailman:///missing.txt')
         self.assertEqual(cm.exception.reason, 'No such file')
 
     def test_shorter_url_error(self):
-        with self.assertRaises(urllib2.URLError) as cm:
+        with self.assertRaises(URLError) as cm:
             self._loader.get('mailman:///')
         self.assertEqual(cm.exception.reason, 'No template specified')
 
     def test_short_url_error(self):
-        with self.assertRaises(urllib2.URLError) as cm:
+        with self.assertRaises(URLError) as cm:
             self._loader.get('mailman://')
         self.assertEqual(cm.exception.reason, 'No template specified')
 
     def test_bad_language(self):
-        with self.assertRaises(urllib2.URLError) as cm:
+        with self.assertRaises(URLError) as cm:
             self._loader.get('mailman:///xx/demo.txt')
         self.assertEqual(cm.exception.reason, 'Bad language or list name')
 
     def test_bad_mailing_list(self):
-        with self.assertRaises(urllib2.URLError) as cm:
+        with self.assertRaises(URLError) as cm:
             self._loader.get('mailman:///missing@example.com/demo.txt')
         self.assertEqual(cm.exception.reason, 'Bad language or list name')
 
     def test_too_many_path_components(self):
-        with self.assertRaises(urllib2.URLError) as cm:
+        with self.assertRaises(URLError) as cm:
             self._loader.get('mailman:///missing@example.com/en/foo/demo.txt')
         self.assertEqual(cm.exception.reason, 'No such file')
 
@@ -135,5 +135,5 @@ class TestTemplateLoader(unittest.TestCase):
         with open(os.path.join(path, 'demo.txt'), 'w') as fp:
             print(test_text, end='', file=fp)
         content = self._loader.get('mailman:///it/demo.txt')
-        self.assertTrue(isinstance(content, unicode))
+        self.assertIsInstance(content, six.text_type)
         self.assertEqual(content, test_text.decode('utf-8'))
diff --git a/src/mailman/archiving/prototype.py b/src/mailman/archiving/prototype.py
index 153c44b69..e564b40b1 100644
--- a/src/mailman/archiving/prototype.py
+++ b/src/mailman/archiving/prototype.py
@@ -30,14 +30,13 @@ import errno
 import logging
 
 from datetime import timedelta
-from mailbox import Maildir
-from urlparse import urljoin
-
 from flufl.lock import Lock, TimeOutError
-from zope.interface import implementer
-
+from mailbox import Maildir
 from mailman.config import config
 from mailman.interfaces.archiver import IArchiver
+from six.moves.urllib_parse import urljoin
+from zope.interface import implementer
+
 
 log = logging.getLogger('mailman.error')
 
diff --git a/src/mailman/archiving/tests/test_prototype.py b/src/mailman/archiving/tests/test_prototype.py
index fba46ea4b..6bc4f25b4 100644
--- a/src/mailman/archiving/tests/test_prototype.py
+++ b/src/mailman/archiving/tests/test_prototype.py
@@ -89,13 +89,13 @@ but the water deserves to be swum.
     def _find(self, path):
         all_filenames = set()
         for dirpath, dirnames, filenames in os.walk(path):
-            if not isinstance(dirpath, unicode):
-                dirpath = unicode(dirpath)
+            if isinstance(dirpath, bytes):
+                dirpath = dirpath.decode('utf-8')
             all_filenames.add(dirpath)
             for filename in filenames:
                 new_filename = filename
-                if not isinstance(filename, unicode):
-                    new_filename = unicode(filename)
+                if isinstance(filename, bytes):
+                    new_filename = filename.decode('utf-8')
                 all_filenames.add(os.path.join(dirpath, new_filename))
         return all_filenames
 
diff --git a/src/mailman/bin/export.py b/src/mailman/bin/export.py
index a5400a9bc..1ee9f31e1 100644
--- a/src/mailman/bin/export.py
+++ b/src/mailman/bin/export.py
@@ -134,7 +134,7 @@ class XMLDumper(object):
             print >> self._fp, '<%s%s/>' % (_name, attrs)
         else:
             # The value might contain angle brackets.
-            value = escape(unicode(_value))
+            value = escape(_value.decode('utf-8'))
             print >> self._fp, '<%s%s>%s</%s>' % (_name, attrs, value, _name)
 
     def _do_list_categories(self, mlist, k, subcat=None):
diff --git a/src/mailman/commands/cli_import.py b/src/mailman/commands/cli_import.py
index 5e25cd4fe..b53faea96 100644
--- a/src/mailman/commands/cli_import.py
+++ b/src/mailman/commands/cli_import.py
@@ -26,16 +26,15 @@ __all__ = [
 
 
 import sys
-import cPickle
-
-from zope.component import getUtility
-from zope.interface import implementer
 
 from mailman.core.i18n import _
 from mailman.database.transaction import transactional
 from mailman.interfaces.command import ICLISubCommand
 from mailman.interfaces.listmanager import IListManager
 from mailman.utilities.importer import import_config_pck, Import21Error
+from six.moves import cPickle
+from zope.component import getUtility
+from zope.interface import implementer
 
 
 
diff --git a/src/mailman/commands/cli_inject.py b/src/mailman/commands/cli_inject.py
index 07ef0ec6c..9339dc074 100644
--- a/src/mailman/commands/cli_inject.py
+++ b/src/mailman/commands/cli_inject.py
@@ -27,14 +27,13 @@ __all__ = [
 
 import sys
 
-from zope.component import getUtility
-from zope.interface import implementer
-
 from mailman.app.inject import inject_text
 from mailman.config import config
 from mailman.core.i18n import _
 from mailman.interfaces.command import ICLISubCommand
 from mailman.interfaces.listmanager import IListManager
+from zope.component import getUtility
+from zope.interface import implementer
 
 
 
@@ -49,7 +48,7 @@ class Inject:
         self.parser = parser
         command_parser.add_argument(
             '-q', '--queue',
-            type=unicode, help=_("""
+            help=_("""
             The name of the queue to inject the message to.  QUEUE must be one
             of the directories inside the qfiles directory.  If omitted, the
             incoming queue is used."""))
@@ -59,7 +58,7 @@ class Inject:
             help=_('Show a list of all available queue names and exit.'))
         command_parser.add_argument(
             '-f', '--filename',
-            type=unicode, help=_("""
+            help=_("""
             Name of file containing the message to inject.  If not given, or
             '-' (without the quotes) standard input is used."""))
         # Required positional argument.
diff --git a/src/mailman/commands/cli_qfile.py b/src/mailman/commands/cli_qfile.py
index 986898bee..c4ff66aea 100644
--- a/src/mailman/commands/cli_qfile.py
+++ b/src/mailman/commands/cli_qfile.py
@@ -25,14 +25,12 @@ __all__ = [
     ]
 
 
-import cPickle
-
-from pprint import PrettyPrinter
-from zope.interface import implementer
-
 from mailman.core.i18n import _
 from mailman.interfaces.command import ICLISubCommand
 from mailman.utilities.interact import interact
+from pprint import PrettyPrinter
+from six.moves import cPickle
+from zope.interface import implementer
 
 
 m = []
diff --git a/src/mailman/commands/docs/echo.rst b/src/mailman/commands/docs/echo.rst
index 32399ebfc..686accf2c 100644
--- a/src/mailman/commands/docs/echo.rst
+++ b/src/mailman/commands/docs/echo.rst
@@ -24,7 +24,7 @@ The original message is ignored, but the results receive the echoed command.
     >>> from mailman.email.message import Message
     >>> print(command.process(mlist, Message(), {}, ('foo', 'bar'), results))
     ContinueProcessing.yes
-    >>> print(unicode(results))
+    >>> print(results.decode('utf-8'))
     The results of your email command are provided below.
     <BLANKLINE>
     echo foo bar
diff --git a/src/mailman/commands/docs/help.rst b/src/mailman/commands/docs/help.rst
index bbd6c8c09..35ba87caa 100644
--- a/src/mailman/commands/docs/help.rst
+++ b/src/mailman/commands/docs/help.rst
@@ -25,7 +25,7 @@ short description of each of them.
     >>> from mailman.email.message import Message
     >>> print(help.process(mlist, Message(), {}, (), results))
     ContinueProcessing.yes
-    >>> print(unicode(results))
+    >>> print(results.decode('utf-8'))
     The results of your email command are provided below.
     <BLANKLINE>
     confirm     - Confirm a subscription request.
@@ -44,19 +44,19 @@ With an argument, you can get more detailed help about a specific command.
     >>> results = Results()
     >>> print(help.process(mlist, Message(), {}, ('help',), results))
     ContinueProcessing.yes
-    >>> print(unicode(results))
+    >>> print(results.decode('utf-8'))
     The results of your email command are provided below.
     <BLANKLINE>
     help [command]
     Get help about available email commands.
     <BLANKLINE>
-    
+
 Some commands have even more detailed help.
 
     >>> results = Results()
     >>> print(help.process(mlist, Message(), {}, ('join',), results))
     ContinueProcessing.yes
-    >>> print(unicode(results))
+    >>> print(results.decode('utf-8'))
     The results of your email command are provided below.
     <BLANKLINE>
     join [digest=<no|mime|plain>]
diff --git a/src/mailman/commands/docs/membership.rst b/src/mailman/commands/docs/membership.rst
index aa3ab97e6..3fe9b05ba 100644
--- a/src/mailman/commands/docs/membership.rst
+++ b/src/mailman/commands/docs/membership.rst
@@ -45,7 +45,7 @@ If that's missing though, then an error is returned.
     >>> from mailman.email.message import Message
     >>> print(join.process(mlist, Message(), {}, (), results))
     ContinueProcessing.no
-    >>> print(unicode(results))
+    >>> print(results.decode('utf-8'))
     The results of your email command are provided below.
     <BLANKLINE>
     join: No valid address found to subscribe
@@ -60,7 +60,7 @@ The ``subscribe`` command is an alias.
     >>> results = Results()
     >>> print(subscribe.process(mlist, Message(), {}, (), results))
     ContinueProcessing.no
-    >>> print(unicode(results))
+    >>> print(results.decode('utf-8'))
     The results of your email command are provided below.
     <BLANKLINE>
     subscribe: No valid address found to subscribe
@@ -79,7 +79,7 @@ When the message has a From field, that address will be subscribed.
     >>> results = Results()
     >>> print(join.process(mlist, msg, {}, (), results))
     ContinueProcessing.yes
-    >>> print(unicode(results))
+    >>> print(results.decode('utf-8'))
     The results of your email command are provided below.
     <BLANKLINE>
     Confirmation email sent to Anne Person <anne@example.com>
@@ -150,7 +150,7 @@ list.
     >>> results = Results()
     >>> print(confirm.process(mlist, msg, {}, (token,), results))
     ContinueProcessing.yes
-    >>> print(unicode(results))
+    >>> print(results.decode('utf-8'))
     The results of your email command are provided below.
     <BLANKLINE>
     Confirmed
@@ -208,7 +208,7 @@ list.
     >>> results = Results()
     >>> print(confirm.process(mlist_2, msg, {}, (token,), results))
     ContinueProcessing.yes
-    >>> print(unicode(results))
+    >>> print(results.decode('utf-8'))
     The results of your email command are provided below.
     <BLANKLINE>
     Confirmed
@@ -241,7 +241,7 @@ is sent a confirmation message for her request.
     >>> results = Results()
     >>> print(leave.process(mlist_2, msg, {}, (), results))
     ContinueProcessing.yes
-    >>> print(unicode(results))
+    >>> print(results.decode('utf-8'))
     The results of your email command are provided below.
     <BLANKLINE>
     Anne Person <anne@example.com> left baker@example.com
@@ -278,7 +278,7 @@ to unsubscribe Anne from the alpha mailing list.
     >>> print(leave.process(mlist, msg, {}, (), results))
     ContinueProcessing.no
 
-    >>> print(unicode(results))
+    >>> print(results.decode('utf-8'))
     The results of your email command are provided below.
     <BLANKLINE>
     Invalid or unverified email address: anne.person@example.org
@@ -299,7 +299,7 @@ unsubscribe her from the list.
     >>> print(leave.process(mlist, msg, {}, (), results))
     ContinueProcessing.yes
 
-    >>> print(unicode(results))
+    >>> print(results.decode('utf-8'))
     The results of your email command are provided below.
     <BLANKLINE>
     Anne Person <anne.person@example.org> left alpha@example.com
@@ -354,7 +354,7 @@ a user of the system.
     >>> print(confirm.process(mlist, msg, {}, (token,), results))
     ContinueProcessing.yes
 
-    >>> print(unicode(results))
+    >>> print(results.decode('utf-8'))
     The results of your email command are provided below.
     <BLANKLINE>
     Confirmed
diff --git a/src/mailman/commands/tests/test_conf.py b/src/mailman/commands/tests/test_conf.py
index 12ed5c537..cc0f61ba2 100644
--- a/src/mailman/commands/tests/test_conf.py
+++ b/src/mailman/commands/tests/test_conf.py
@@ -31,9 +31,9 @@ import mock
 import tempfile
 import unittest
 
-from StringIO import StringIO
 from mailman.commands.cli_conf import Conf
 from mailman.testing.layers import ConfigLayer
+from six import StringIO
 
 
 
diff --git a/src/mailman/commands/tests/test_help.py b/src/mailman/commands/tests/test_help.py
index 3c7d1ae9f..74eaae84e 100644
--- a/src/mailman/commands/tests/test_help.py
+++ b/src/mailman/commands/tests/test_help.py
@@ -47,11 +47,11 @@ class TestHelp(unittest.TestCase):
     def test_too_many_arguments(self):
         # Error message when too many help arguments are given.
         results = Results()
-        status = self._help.process(self._mlist, Message(), {}, 
+        status = self._help.process(self._mlist, Message(), {},
                                     ('more', 'than', 'one'),
                                     results)
         self.assertEqual(status, ContinueProcessing.no)
-        self.assertEqual(unicode(results), """\
+        self.assertEqual(results.decode('utf-8'), """\
 The results of your email command are provided below.
 
 help: too many arguments: more than one
@@ -60,10 +60,10 @@ help: too many arguments: more than one
     def test_no_such_command(self):
         # Error message when asking for help on an existent command.
         results = Results()
-        status = self._help.process(self._mlist, Message(), {}, 
+        status = self._help.process(self._mlist, Message(), {},
                                     ('doesnotexist',), results)
         self.assertEqual(status, ContinueProcessing.no)
-        self.assertEqual(unicode(results), """\
+        self.assertEqual(results.decode('utf-8'), """\
 The results of your email command are provided below.
 
 help: no such command: doesnotexist
diff --git a/src/mailman/config/config.py b/src/mailman/config/config.py
index 649d6c5e1..c92485176 100644
--- a/src/mailman/config/config.py
+++ b/src/mailman/config/config.py
@@ -30,11 +30,12 @@ __all__ = [
 import os
 import sys
 
-from ConfigParser import SafeConfigParser
 from flufl.lock import Lock
 from lazr.config import ConfigSchema, as_boolean
-from pkg_resources import resource_stream, resource_string
+from pkg_resources import resource_filename, resource_string
+from six.moves.configparser import ConfigParser, RawConfigParser
 from string import Template
+from unittest.mock import patch
 from zope.component import getUtility
 from zope.event import notify
 from zope.interface import implementer
@@ -66,6 +67,11 @@ MAILMAN_CFG_TEMPLATE = """\
 # enabled: yes
 # recipient: your.address@your.domain"""
 
+class _NonStrictRawConfigParser(RawConfigParser):
+    def __init__(self, *args, **kws):
+        kws['strict'] = False
+        super().__init__(*args, **kws)
+
 
 
 @implementer(IConfiguration)
@@ -99,30 +105,27 @@ class Configuration:
 
     def load(self, filename=None):
         """Load the configuration from the schema and config files."""
-        schema_file = config_file = None
-        try:
-            schema_file = resource_stream('mailman.config', 'schema.cfg')
-            schema = ConfigSchema('schema.cfg', schema_file)
-            # If a configuration file was given, load it now too.  First, load
-            # the absolute minimum default configuration, then if a
-            # configuration filename was given by the user, push it.
-            config_file = resource_stream('mailman.config', 'mailman.cfg')
-            self._config = schema.loadFile(config_file, 'mailman.cfg')
-            if filename is not None:
-                self.filename = filename
-                with open(filename) as user_config:
-                    self._config.push(filename, user_config.read())
-        finally:
-            if schema_file:
-                schema_file.close()
-            if config_file:
-                config_file.close()
-        self._post_process()
+        schema_file = resource_filename('mailman.config', 'schema.cfg')
+        schema = ConfigSchema(schema_file)
+        # If a configuration file was given, load it now too.  First, load
+        # the absolute minimum default configuration, then if a
+        # configuration filename was given by the user, push it.
+        config_file = resource_filename('mailman.config', 'mailman.cfg')
+        self._config = schema.load(config_file)
+        if filename is not None:
+            self.filename = filename
+            with open(filename) as user_config:
+                self.push(filename, user_config.read())
 
     def push(self, config_name, config_string):
         """Push a new configuration onto the stack."""
         self._clear()
-        self._config.push(config_name, config_string)
+        # In Python 3, the RawConfigParser() must be created with
+        # strict=False, otherwise we'll get a DuplicateSectionError.
+        # See https://bugs.launchpad.net/lazr.config/+bug/1397779
+        with patch('lazr.config._config.RawConfigParser',
+                   _NonStrictRawConfigParser):
+            self._config.push(config_name, config_string)
         self._post_process()
 
     def pop(self, config_name):
@@ -305,7 +308,7 @@ def external_configuration(path):
     """
     # Is the context coming from a file system or Python path?
     cfg_path = expand_path(path)
-    parser = SafeConfigParser()
+    parser = ConfigParser()
     files = parser.read(cfg_path)
     if files != [cfg_path]:
         raise MissingConfigurationFileError(path)
diff --git a/src/mailman/config/tests/test_configuration.py b/src/mailman/config/tests/test_configuration.py
index f3a49d64f..b411f9615 100644
--- a/src/mailman/config/tests/test_configuration.py
+++ b/src/mailman/config/tests/test_configuration.py
@@ -28,6 +28,7 @@ __all__ = [
 
 
 import os
+import six
 import mock
 import tempfile
 import unittest
@@ -79,12 +80,12 @@ class TestExternal(unittest.TestCase):
     def test_load_external_by_filename_as_string(self):
         filename = resource_filename('mailman.config', 'postfix.cfg')
         contents = load_external(filename, encoding='utf-8')
-        self.assertIsInstance(contents, unicode)
+        self.assertIsInstance(contents, six.text_type)
         self.assertEqual(contents[:9], '[postfix]')
 
     def test_load_external_by_path_as_string(self):
         contents = load_external('python:mailman.config.postfix', 'utf-8')
-        self.assertIsInstance(contents, unicode)
+        self.assertIsInstance(contents, six.text_type)
         self.assertEqual(contents[:9], '[postfix]')
 
     def test_external_configuration_by_filename(self):
diff --git a/src/mailman/core/initialize.py b/src/mailman/core/initialize.py
index c2395db10..6c7196990 100644
--- a/src/mailman/core/initialize.py
+++ b/src/mailman/core/initialize.py
@@ -39,7 +39,7 @@ __all__ = [
 import os
 import sys
 
-from pkg_resources import resource_string
+from pkg_resources import resource_string as resource_bytes
 from zope.component import getUtility
 from zope.configuration import xmlconfig
 
@@ -109,8 +109,8 @@ def initialize_1(config_path=None):
     :param config_path: The path to the configuration file.
     :type config_path: string
     """
-    zcml = resource_string('mailman.config', 'configure.zcml')
-    xmlconfig.string(zcml)
+    zcml = resource_bytes('mailman.config', 'configure.zcml')
+    xmlconfig.string(zcml.decode('utf-8'))
     # By default, set the umask so that only owner and group can read and
     # write our files.  Specifically we must have g+rw and we probably want
     # o-rwx although I think in most cases it doesn't hurt if other can read
diff --git a/src/mailman/core/runner.py b/src/mailman/core/runner.py
index 81a2ea3d1..d6aad2b07 100644
--- a/src/mailman/core/runner.py
+++ b/src/mailman/core/runner.py
@@ -30,12 +30,7 @@ import signal
 import logging
 import traceback
 
-from cStringIO import StringIO
 from lazr.config import as_boolean, as_timedelta
-from zope.component import getUtility
-from zope.event import notify
-from zope.interface import implementer
-
 from mailman.config import config
 from mailman.core.i18n import _
 from mailman.core.logging import reopen
@@ -44,6 +39,10 @@ from mailman.interfaces.languages import ILanguageManager
 from mailman.interfaces.listmanager import IListManager
 from mailman.interfaces.runner import IRunner, RunnerCrashEvent
 from mailman.utilities.string import expand
+from six.moves import cStringIO as StringIO
+from zope.component import getUtility
+from zope.event import notify
+from zope.interface import implementer
 
 
 dlog = logging.getLogger('mailman.debug')
@@ -218,11 +217,11 @@ class Runner:
         # them out of our sight.
         #
         # Find out which mailing list this message is destined for.
+        mlist = None
         missing = object()
         listname = msgdata.get('listname', missing)
-        mlist = (None
-                 if listname is missing
-                 else getUtility(IListManager).get(unicode(listname)))
+        if listname is missing:
+            mlist = getUtility(IListManager).get(listname.decode('utf-8'))
         if mlist is None:
             elog.error(
                 '%s runner "%s" shunting message for missing list: %s',
diff --git a/src/mailman/core/switchboard.py b/src/mailman/core/switchboard.py
index 2e8ef24a7..78a12616e 100644
--- a/src/mailman/core/switchboard.py
+++ b/src/mailman/core/switchboard.py
@@ -37,22 +37,22 @@ import os
 import time
 import email
 import pickle
-import cPickle
 import hashlib
 import logging
 
-from zope.interface import implementer
-
 from mailman.config import config
 from mailman.email.message import Message
 from mailman.interfaces.configuration import ConfigurationUpdatedEvent
 from mailman.interfaces.switchboard import ISwitchboard
 from mailman.utilities.filesystem import makedirs
 from mailman.utilities.string import expand
+from six.moves import cPickle
+from zope.interface import implementer
 
 
-# 20 bytes of all bits set, maximum hashlib.sha.digest() value.
-shamax = 0xffffffffffffffffffffffffffffffffffffffffL
+# 20 bytes of all bits set, maximum hashlib.sha.digest() value.  We do it this
+# way for Python 2/3 compatibility.
+shamax = int('0xffffffffffffffffffffffffffffffffffffffff', 16)
 # Small increment to add to time in case two entries have the same time.  This
 # prevents skipping one of two entries with the same time until the next pass.
 DELTA = .0001
@@ -92,7 +92,7 @@ class Switchboard:
         self.queue_directory = queue_directory
         # If configured to, create the directory if it doesn't yet exist.
         if config.create_paths:
-            makedirs(self.queue_directory, 0770)
+            makedirs(self.queue_directory, 0o770)
         # Fast track for no slices
         self._lower = None
         self._upper = None
@@ -123,7 +123,7 @@ class Switchboard:
             msgsave = cPickle.dumps(_msg, protocol)
         # listname is unicode but the input to the hash function must be an
         # 8-bit string (eventually, a bytes object).
-        hashfood = msgsave + listname.encode('utf-8') + repr(now)
+        hashfood = msgsave + listname + repr(now)
         # Encode the current time into the file name for FIFO sorting.  The
         # file name consists of two parts separated by a '+': the received
         # time for this message (i.e. when it first showed up on this system)
@@ -207,13 +207,13 @@ class Switchboard:
             # Throw out any files which don't match our bitrange.  BAW: test
             # performance and end-cases of this algorithm.  MAS: both
             # comparisons need to be <= to get complete range.
-            if lower is None or (lower <= long(digest, 16) <= upper):
+            if lower is None or (lower <= int(digest, 16) <= upper):
                 key = float(when)
                 while key in times:
                     key += DELTA
                 times[key] = filebase
         # FIFO sort
-        return [times[key] for key in sorted(times)]
+        return [times[k] for k in sorted(times)]
 
     def recover_backup_files(self):
         """See `ISwitchboard`."""
@@ -228,7 +228,8 @@ class Switchboard:
             dst = os.path.join(self.queue_directory, filebase + '.pck')
             with open(src, 'rb+') as fp:
                 try:
-                    msg = cPickle.load(fp)
+                    # Throw away the message object.
+                    cPickle.load(fp)
                     data_pos = fp.tell()
                     data = cPickle.load(fp)
                 except Exception as error:
diff --git a/src/mailman/database/sqlite.py b/src/mailman/database/sqlite.py
index db7860390..8540846e1 100644
--- a/src/mailman/database/sqlite.py
+++ b/src/mailman/database/sqlite.py
@@ -28,7 +28,7 @@ __all__ = [
 import os
 
 from mailman.database.base import SABaseDatabase
-from urlparse import urlparse
+from six.moves.urllib_parse import urlparse
 
 
 
diff --git a/src/mailman/email/message.py b/src/mailman/email/message.py
index f3a44e63c..4d26ca9c4 100644
--- a/src/mailman/email/message.py
+++ b/src/mailman/email/message.py
@@ -56,15 +56,15 @@ class Message(email.message.Message):
     def __getitem__(self, key):
         # Ensure that header values are unicodes.
         value = email.message.Message.__getitem__(self, key)
-        if isinstance(value, str):
-            return unicode(value, 'ascii')
+        if isinstance(value, bytes):
+            return value.decode('ascii')
         return value
 
     def get(self, name, failobj=None):
         # Ensure that header values are unicodes.
         value = email.message.Message.get(self, name, failobj)
-        if isinstance(value, str):
-            return unicode(value, 'ascii')
+        if isinstance(value, bytes):
+            return value.decode('ascii')
         return value
 
     def get_all(self, name, failobj=None):
@@ -73,7 +73,7 @@ class Message(email.message.Message):
         all_values = email.message.Message.get_all(self, name, missing)
         if all_values is missing:
             return failobj
-        return [(unicode(value, 'ascii') if isinstance(value, str) else value)
+        return [(value.decode('ascii') if isinstance(value, bytes) else value)
                 for value in all_values]
 
     # BAW: For debugging w/ bin/dumpdb.  Apparently pprint uses repr.
diff --git a/src/mailman/handlers/cook_headers.py b/src/mailman/handlers/cook_headers.py
index d5d096448..5fdfc238b 100644
--- a/src/mailman/handlers/cook_headers.py
+++ b/src/mailman/handlers/cook_headers.py
@@ -201,7 +201,7 @@ def prefix_subject(mlist, msg, msgdata):
     # range.  It is safe to use unicode string when manupilating header
     # contents with re module.  It would be best to return unicode in
     # ch_oneline() but here is temporary solution.
-    subject = unicode(subject, cset)
+    subject = subject.decode(cset)
     # If the subject_prefix contains '%d', it is replaced with the
     # mailing list sequential number.  Sequential number format allows
     # '%d' or '%05d' like pattern.
@@ -270,7 +270,7 @@ def ch_oneline(headerstr):
         else:
             cset = 'utf-8'
         h = make_header(d)
-        ustr = unicode(h)
+        ustr = h.decode('utf-8')
         oneline = ''.join(ustr.splitlines())
         return oneline.encode(cset, 'replace'), cset
     except (LookupError, UnicodeError, ValueError, HeaderParseError):
diff --git a/src/mailman/handlers/decorate.py b/src/mailman/handlers/decorate.py
index bf8454232..03f0c009f 100644
--- a/src/mailman/handlers/decorate.py
+++ b/src/mailman/handlers/decorate.py
@@ -31,15 +31,14 @@ import re
 import logging
 
 from email.mime.text import MIMEText
-from urllib2 import URLError
-from zope.component import getUtility
-from zope.interface import implementer
-
 from mailman.core.i18n import _
 from mailman.email.message import Message
 from mailman.interfaces.handler import IHandler
 from mailman.interfaces.templates import ITemplateLoader
 from mailman.utilities.string import expand
+from six.moves.urllib_error import URLError
+from zope.component import getUtility
+from zope.interface import implementer
 
 
 log = logging.getLogger('mailman.error')
diff --git a/src/mailman/handlers/docs/subject-munging.rst b/src/mailman/handlers/docs/subject-munging.rst
index 538ad99c7..072e80d17 100644
--- a/src/mailman/handlers/docs/subject-munging.rst
+++ b/src/mailman/handlers/docs/subject-munging.rst
@@ -124,7 +124,7 @@ set than the encoded header.
     >>> process(mlist, msg, {})
     >>> print(msg['subject'])
     [XTest] =?iso-2022-jp?b?GyRCJWEhPCVrJV4lcxsoQg==?=
-    >>> unicode(msg['subject'])
+    >>> msg['subject'].decode('utf-8')
     u'[XTest] \u30e1\u30fc\u30eb\u30de\u30f3'
 
 
@@ -180,7 +180,7 @@ in the subject prefix, and the subject is encoded non-ASCII.
     >>> process(mlist, msg, {})
     >>> print(msg['subject'])
     [XTest 456] =?iso-2022-jp?b?GyRCJWEhPCVrJV4lcxsoQg==?=
-    >>> unicode(msg['subject'])
+    >>> msg['subject'].decode('utf-8')
     u'[XTest 456] \u30e1\u30fc\u30eb\u30de\u30f3'
 
 Even more fun is when the internationalized ``Subject`` header already has a
@@ -194,10 +194,8 @@ prefix, possibly with a different posting number.
     >>> print(msg['subject'])
     [XTest 456] Re: =?iso-2022-jp?b?GyRCJWEhPCVrJV4lcxsoQg==?=
 
-..
- # XXX This requires Python email patch #1681333 to succeed.
- #    >>> unicode(msg['subject'])
- #    u'[XTest 456] Re: \u30e1\u30fc\u30eb\u30de\u30f3'
+    >>> msg['subject'].decode('utf-8')
+    u'[XTest 456] Re: \u30e1\u30fc\u30eb\u30de\u30f3'
 
 As before, old style subject prefixes are re-ordered.
 
@@ -210,10 +208,8 @@ As before, old style subject prefixes are re-ordered.
     [XTest 456] Re:
       =?iso-2022-jp?b?GyRCJWEhPCVrJV4lcxsoQg==?=
 
-..
- # XXX This requires Python email patch #1681333 to succeed.
- #    >>> unicode(msg['subject'])
- #    u'[XTest 456] Re: \u30e1\u30fc\u30eb\u30de\u30f3'
+    >>> msg['subject'].decode('utf-8')
+    u'[XTest 456] Re: \u30e1\u30fc\u30eb\u30de\u30f3'
 
 
 In this test case, we get an extra space between the prefix and the original
diff --git a/src/mailman/handlers/tests/test_recipients.py b/src/mailman/handlers/tests/test_recipients.py
index afe533a7e..8f2a9d47d 100644
--- a/src/mailman/handlers/tests/test_recipients.py
+++ b/src/mailman/handlers/tests/test_recipients.py
@@ -26,15 +26,16 @@ __all__ = [
     ]
 
 
+import six
 import unittest
 
-from zope.component import getUtility
 from mailman.app.lifecycle import create_list
 from mailman.config import config
 from mailman.interfaces.member import DeliveryMode, DeliveryStatus, MemberRole
 from mailman.interfaces.usermanager import IUserManager
 from mailman.testing.helpers import specialized_message_from_string as mfs
 from mailman.testing.layers import ConfigLayer
+from zope.component import getUtility
 
 
 
@@ -218,4 +219,4 @@ site_owner: siteadmin@example.com
         finally:
             config.pop('test_site_admin_unicode')
         self.assertEqual(len(msgdata['recipients']), 1)
-        self.assertIsInstance(list(msgdata['recipients'])[0], unicode)
+        self.assertIsInstance(list(msgdata['recipients'])[0], six.text_type)
diff --git a/src/mailman/model/domain.py b/src/mailman/model/domain.py
index 8290cb755..a9020e816 100644
--- a/src/mailman/model/domain.py
+++ b/src/mailman/model/domain.py
@@ -26,17 +26,16 @@ __all__ = [
     ]
 
 
-from sqlalchemy import Column, Integer, Unicode
-from urlparse import urljoin, urlparse
-from zope.event import notify
-from zope.interface import implementer
-
 from mailman.database.model import Model
 from mailman.database.transaction import dbconnection
 from mailman.interfaces.domain import (
     BadDomainSpecificationError, DomainCreatedEvent, DomainCreatingEvent,
     DomainDeletedEvent, DomainDeletingEvent, IDomain, IDomainManager)
 from mailman.model.mailinglist import MailingList
+from six.moves.urllib_parse import urljoin, urlparse
+from sqlalchemy import Column, Integer, Unicode
+from zope.event import notify
+from zope.interface import implementer
 
 
 
diff --git a/src/mailman/model/mailinglist.py b/src/mailman/model/mailinglist.py
index 761a78b94..c55786fe8 100644
--- a/src/mailman/model/mailinglist.py
+++ b/src/mailman/model/mailinglist.py
@@ -27,16 +27,6 @@ __all__ = [
 
 import os
 
-from sqlalchemy import (
-    Boolean, Column, DateTime, Float, ForeignKey, Integer, Interval,
-    LargeBinary, PickleType, Unicode)
-from sqlalchemy.event import listen
-from sqlalchemy.orm import relationship
-from urlparse import urljoin
-from zope.component import getUtility
-from zope.event import notify
-from zope.interface import implementer
-
 from mailman.config import config
 from mailman.database.model import Model
 from mailman.database.transaction import dbconnection
@@ -65,6 +55,15 @@ from mailman.model.mime import ContentFilter
 from mailman.model.preferences import Preferences
 from mailman.utilities.filesystem import makedirs
 from mailman.utilities.string import expand
+from six.moves.urllib_parse import urljoin
+from sqlalchemy import (
+    Boolean, Column, DateTime, Float, ForeignKey, Integer, Interval,
+    LargeBinary, PickleType, Unicode)
+from sqlalchemy.event import listen
+from sqlalchemy.orm import relationship
+from zope.component import getUtility
+from zope.event import notify
+from zope.interface import implementer
 
 
 SPACE = ' '
diff --git a/src/mailman/model/messagestore.py b/src/mailman/model/messagestore.py
index 19fa8133f..19b87c610 100644
--- a/src/mailman/model/messagestore.py
+++ b/src/mailman/model/messagestore.py
@@ -27,16 +27,15 @@ __all__ = [
 import os
 import errno
 import base64
+import pickle
 import hashlib
-import cPickle as pickle
-
-from zope.interface import implementer
 
 from mailman.config import config
 from mailman.database.transaction import dbconnection
 from mailman.interfaces.messages import IMessageStore
 from mailman.model.message import Message
 from mailman.utilities.filesystem import makedirs
+from zope.interface import implementer
 
 
 # It could be very bad if you have already stored files and you change this
diff --git a/src/mailman/model/requests.py b/src/mailman/model/requests.py
index 6b130196d..24575d3c8 100644
--- a/src/mailman/model/requests.py
+++ b/src/mailman/model/requests.py
@@ -24,18 +24,19 @@ __all__ = [
     ]
 
 
-from cPickle import dumps, loads
-from datetime import timedelta
-from sqlalchemy import Column, ForeignKey, Integer, LargeBinary, Unicode
-from sqlalchemy.orm import relationship
-from zope.component import getUtility
-from zope.interface import implementer
+import six
 
+from datetime import timedelta
 from mailman.database.model import Model
 from mailman.database.transaction import dbconnection
 from mailman.database.types import Enum
 from mailman.interfaces.pending import IPendable, IPendings
 from mailman.interfaces.requests import IListRequests, RequestType
+from six.moves.cPickle import dumps, loads
+from sqlalchemy import Column, ForeignKey, Integer, LargeBinary, Unicode
+from sqlalchemy.orm import relationship
+from zope.component import getUtility
+from zope.interface import implementer
 
 
 
@@ -50,8 +51,8 @@ class DataPendable(dict):
         # such a way that it will be properly reconstituted when unpended.
         clean_mapping = {}
         for key, value in mapping.items():
-            assert isinstance(key, basestring)
-            if not isinstance(value, unicode):
+            assert isinstance(key, six.string_types)
+            if not isinstance(value, six.text_type):
                 key = '_pck_' + key
                 value = dumps(value).decode('raw-unicode-escape')
             clean_mapping[key] = value
diff --git a/src/mailman/options.py b/src/mailman/options.py
index a4f553a09..07565f611 100644
--- a/src/mailman/options.py
+++ b/src/mailman/options.py
@@ -42,7 +42,7 @@ from mailman.version import MAILMAN_VERSION
 
 def check_unicode(option, opt, value):
     """Check that the value is a unicode string."""
-    if isinstance(value, unicode):
+    if not isinstance(value, bytes):
         return value
     try:
         return value.decode(sys.getdefaultencoding())
diff --git a/src/mailman/rest/addresses.py b/src/mailman/rest/addresses.py
index fa3d099b6..7923d8bf9 100644
--- a/src/mailman/rest/addresses.py
+++ b/src/mailman/rest/addresses.py
@@ -27,6 +27,8 @@ __all__ = [
     ]
 
 
+import six
+
 from operator import attrgetter
 from zope.component import getUtility
 
@@ -186,8 +188,8 @@ class UserAddresses(_AddressBase):
             not_found(response)
             return
         user_manager = getUtility(IUserManager)
-        validator = Validator(email=unicode,
-                              display_name=unicode,
+        validator = Validator(email=six.text_type,
+                              display_name=six.text_type,
                               _optional=('display_name',))
         try:
             address = user_manager.create_address(**validator(request))
diff --git a/src/mailman/rest/configuration.py b/src/mailman/rest/configuration.py
index b432268c7..6ea78f90e 100644
--- a/src/mailman/rest/configuration.py
+++ b/src/mailman/rest/configuration.py
@@ -25,6 +25,8 @@ __all__ = [
     ]
 
 
+import six
+
 from lazr.config import as_boolean, as_timedelta
 from mailman.config import config
 from mailman.core.errors import (
@@ -61,7 +63,7 @@ class AcceptableAliases(GetterSetter):
         alias_set = IAcceptableAliasSet(mlist)
         alias_set.clear()
         for alias in value:
-            alias_set.add(unicode(alias))
+            alias_set.add(alias.decode('utf-8'))
 
 
 
@@ -71,13 +73,13 @@ class AcceptableAliases(GetterSetter):
 def pipeline_validator(pipeline_name):
     """Convert the pipeline name to a string, but only if it's known."""
     if pipeline_name in config.pipelines:
-        return unicode(pipeline_name)
+        return pipeline_name.decode('utf-8')
     raise ValueError('Unknown pipeline: {}'.format(pipeline_name))
 
 
 def list_of_unicode(values):
     """Turn a list of things into a list of unicodes."""
-    return [unicode(value) for value in values]
+    return [value.decode('utf-8') for value in values]
 
 
 
@@ -106,9 +108,9 @@ ATTRIBUTES = dict(
     autorespond_postings=GetterSetter(enum_validator(ResponseAction)),
     autorespond_requests=GetterSetter(enum_validator(ResponseAction)),
     autoresponse_grace_period=GetterSetter(as_timedelta),
-    autoresponse_owner_text=GetterSetter(unicode),
-    autoresponse_postings_text=GetterSetter(unicode),
-    autoresponse_request_text=GetterSetter(unicode),
+    autoresponse_owner_text=GetterSetter(six.text_type),
+    autoresponse_postings_text=GetterSetter(six.text_type),
+    autoresponse_request_text=GetterSetter(six.text_type),
     archive_policy=GetterSetter(enum_validator(ArchivePolicy)),
     bounces_address=GetterSetter(None),
     collapse_alternatives=GetterSetter(as_boolean),
@@ -116,7 +118,7 @@ ATTRIBUTES = dict(
     created_at=GetterSetter(None),
     default_member_action=GetterSetter(enum_validator(Action)),
     default_nonmember_action=GetterSetter(enum_validator(Action)),
-    description=GetterSetter(unicode),
+    description=GetterSetter(six.text_type),
     digest_last_sent_at=GetterSetter(None),
     digest_size_threshold=GetterSetter(float),
     filter_content=GetterSetter(as_boolean),
@@ -135,21 +137,21 @@ ATTRIBUTES = dict(
     post_id=GetterSetter(None),
     posting_address=GetterSetter(None),
     posting_pipeline=GetterSetter(pipeline_validator),
-    display_name=GetterSetter(unicode),
+    display_name=GetterSetter(six.text_type),
     reply_goes_to_list=GetterSetter(enum_validator(ReplyToMunging)),
-    reply_to_address=GetterSetter(unicode),
+    reply_to_address=GetterSetter(six.text_type),
     request_address=GetterSetter(None),
     scheme=GetterSetter(None),
     send_welcome_message=GetterSetter(as_boolean),
-    subject_prefix=GetterSetter(unicode),
+    subject_prefix=GetterSetter(six.text_type),
     volume=GetterSetter(None),
     web_host=GetterSetter(None),
-    welcome_message_uri=GetterSetter(unicode),
+    welcome_message_uri=GetterSetter(six.text_type),
     )
 
 
 VALIDATORS = ATTRIBUTES.copy()
-for attribute, gettersetter in VALIDATORS.items():
+for attribute, gettersetter in list(VALIDATORS.items()):
     if gettersetter.decoder is None:
         del VALIDATORS[attribute]
 
diff --git a/src/mailman/rest/docs/helpers.rst b/src/mailman/rest/docs/helpers.rst
index 5bcf5cad4..2dd65bbb8 100644
--- a/src/mailman/rest/docs/helpers.rst
+++ b/src/mailman/rest/docs/helpers.rst
@@ -69,8 +69,9 @@ Another helper unpacks ``POST`` and ``PUT`` request variables, validating and
 converting their values.
 ::
 
+    >>> import six
     >>> from mailman.rest.validator import Validator
-    >>> validator = Validator(one=int, two=unicode, three=bool)
+    >>> validator = Validator(one=int, two=six.text_type, three=bool)
 
     >>> class FakeRequest:
     ...     params = None
@@ -119,7 +120,7 @@ Extra keys are also not allowed.
 However, if optional keys are missing, it's okay.
 ::
 
-    >>> validator = Validator(one=int, two=unicode, three=bool,
+    >>> validator = Validator(one=int, two=six.text_type, three=bool,
     ...                       four=int, five=int,
     ...                       _optional=('four', 'five'))
 
diff --git a/src/mailman/rest/domains.py b/src/mailman/rest/domains.py
index 5d36dcab9..bd221abeb 100644
--- a/src/mailman/rest/domains.py
+++ b/src/mailman/rest/domains.py
@@ -26,6 +26,8 @@ __all__ = [
     ]
 
 
+import six
+
 from mailman.interfaces.domain import (
     BadDomainSpecificationError, IDomainManager)
 from mailman.rest.helpers import (
@@ -99,10 +101,10 @@ class AllDomains(_DomainBase):
         """Create a new domain."""
         domain_manager = getUtility(IDomainManager)
         try:
-            validator = Validator(mail_host=unicode,
-                                  description=unicode,
-                                  base_url=unicode,
-                                  contact_address=unicode,
+            validator = Validator(mail_host=six.text_type,
+                                  description=six.text_type,
+                                  base_url=six.text_type,
+                                  contact_address=six.text_type,
                                   _optional=('description', 'base_url',
                                              'contact_address'))
             domain = domain_manager.add(**validator(request))
diff --git a/src/mailman/rest/lists.py b/src/mailman/rest/lists.py
index 580b6e898..feaa96323 100644
--- a/src/mailman/rest/lists.py
+++ b/src/mailman/rest/lists.py
@@ -30,6 +30,8 @@ __all__ = [
     ]
 
 
+import six
+
 from lazr.config import as_boolean
 from operator import attrgetter
 from zope.component import getUtility
@@ -204,8 +206,8 @@ class AllLists(_ListBase):
     def on_post(self, request, response):
         """Create a new mailing list."""
         try:
-            validator = Validator(fqdn_listname=unicode,
-                                  style_name=unicode,
+            validator = Validator(fqdn_listname=six.text_type,
+                                  style_name=six.text_type,
                                   _optional=('style_name',))
             mlist = create_list(**validator(request))
         except ListAlreadyExistsError:
diff --git a/src/mailman/rest/members.py b/src/mailman/rest/members.py
index 4d1c87b73..b63f65658 100644
--- a/src/mailman/rest/members.py
+++ b/src/mailman/rest/members.py
@@ -28,6 +28,8 @@ __all__ = [
     ]
 
 
+import six
+
 from uuid import UUID
 from operator import attrgetter
 from zope.component import getUtility
@@ -176,7 +178,7 @@ class AMember(_MemberBase):
             return
         try:
             values = Validator(
-                address=unicode,
+                address=six.text_type,
                 delivery_mode=enum_validator(DeliveryMode),
                 _optional=('address', 'delivery_mode'))(request)
         except ValueError as error:
@@ -207,9 +209,9 @@ class AllMembers(_MemberBase):
         service = getUtility(ISubscriptionService)
         try:
             validator = Validator(
-                list_id=unicode,
+                list_id=six.text_type,
                 subscriber=subscriber_validator,
-                display_name=unicode,
+                display_name=six.text_type,
                 delivery_mode=enum_validator(DeliveryMode),
                 role=enum_validator(MemberRole),
                 _optional=('delivery_mode', 'display_name', 'role'))
@@ -256,8 +258,8 @@ class FindMembers(_MemberBase):
         """Find a member"""
         service = getUtility(ISubscriptionService)
         validator = Validator(
-            list_id=unicode,
-            subscriber=unicode,
+            list_id=six.text_type,
+            subscriber=six.text_type,
             role=enum_validator(MemberRole),
             _optional=('list_id', 'subscriber', 'role'))
         try:
diff --git a/src/mailman/rest/tests/test_addresses.py b/src/mailman/rest/tests/test_addresses.py
index f4aeb3013..29e09355e 100644
--- a/src/mailman/rest/tests/test_addresses.py
+++ b/src/mailman/rest/tests/test_addresses.py
@@ -27,15 +27,14 @@ __all__ = [
 
 import unittest
 
-from urllib2 import HTTPError
-from zope.component import getUtility
-
 from mailman.app.lifecycle import create_list
 from mailman.database.transaction import transaction
 from mailman.interfaces.usermanager import IUserManager
 from mailman.testing.helpers import call_api
 from mailman.testing.layers import RESTLayer
 from mailman.utilities.datetime import now
+from six.moves.urllib_error import HTTPError
+from zope.component import getUtility
 
 
 
diff --git a/src/mailman/rest/tests/test_domains.py b/src/mailman/rest/tests/test_domains.py
index 44cf11ef3..48f9c4fe3 100644
--- a/src/mailman/rest/tests/test_domains.py
+++ b/src/mailman/rest/tests/test_domains.py
@@ -27,14 +27,13 @@ __all__ = [
 
 import unittest
 
-from urllib2 import HTTPError
-from zope.component import getUtility
-
 from mailman.app.lifecycle import create_list
 from mailman.database.transaction import transaction
 from mailman.interfaces.listmanager import IListManager
 from mailman.testing.helpers import call_api
 from mailman.testing.layers import RESTLayer
+from six.moves.urllib_error import HTTPError
+from zope.component import getUtility
 
 
 
diff --git a/src/mailman/rest/tests/test_lists.py b/src/mailman/rest/tests/test_lists.py
index ba6f6ea59..e8cc54d4b 100644
--- a/src/mailman/rest/tests/test_lists.py
+++ b/src/mailman/rest/tests/test_lists.py
@@ -30,14 +30,13 @@ __all__ = [
 
 import unittest
 
-from urllib2 import HTTPError
-from zope.component import getUtility
-
 from mailman.app.lifecycle import create_list
 from mailman.database.transaction import transaction
 from mailman.interfaces.usermanager import IUserManager
 from mailman.testing.helpers import call_api
 from mailman.testing.layers import RESTLayer
+from six.moves.urllib_error import HTTPError
+from zope.component import getUtility
 
 
 
diff --git a/src/mailman/rest/tests/test_membership.py b/src/mailman/rest/tests/test_membership.py
index 3c7d0520b..6b40fbb01 100644
--- a/src/mailman/rest/tests/test_membership.py
+++ b/src/mailman/rest/tests/test_membership.py
@@ -28,9 +28,6 @@ __all__ = [
 
 import unittest
 
-from urllib2 import HTTPError
-from zope.component import getUtility
-
 from mailman.app.lifecycle import create_list
 from mailman.config import config
 from mailman.database.transaction import transaction
@@ -41,6 +38,8 @@ from mailman.testing.helpers import (
 from mailman.runners.incoming import IncomingRunner
 from mailman.testing.layers import ConfigLayer, RESTLayer
 from mailman.utilities.datetime import now
+from six.moves.urllib_error import HTTPError
+from zope.component import getUtility
 
 
 
diff --git a/src/mailman/rest/tests/test_moderation.py b/src/mailman/rest/tests/test_moderation.py
index c0ec4755a..0e2528b0f 100644
--- a/src/mailman/rest/tests/test_moderation.py
+++ b/src/mailman/rest/tests/test_moderation.py
@@ -26,8 +26,6 @@ __all__ = [
 
 import unittest
 
-from urllib2 import HTTPError
-
 from mailman.app.lifecycle import create_list
 from mailman.app.moderator import hold_message, hold_subscription
 from mailman.config import config
@@ -36,6 +34,7 @@ from mailman.interfaces.member import DeliveryMode
 from mailman.testing.helpers import (
     call_api, specialized_message_from_string as mfs)
 from mailman.testing.layers import RESTLayer
+from six.moves.urllib_error import HTTPError
 
 
 
diff --git a/src/mailman/rest/tests/test_preferences.py b/src/mailman/rest/tests/test_preferences.py
index 91a066cff..06e0b035b 100644
--- a/src/mailman/rest/tests/test_preferences.py
+++ b/src/mailman/rest/tests/test_preferences.py
@@ -32,7 +32,7 @@ from mailman.database.transaction import transaction
 from mailman.interfaces.usermanager import IUserManager
 from mailman.testing.helpers import call_api
 from mailman.testing.layers import RESTLayer
-from urllib2 import HTTPError
+from six.moves.urllib_error import HTTPError
 from zope.component import getUtility
 
 
diff --git a/src/mailman/rest/tests/test_root.py b/src/mailman/rest/tests/test_root.py
index d4d25ede0..c5787bcb1 100644
--- a/src/mailman/rest/tests/test_root.py
+++ b/src/mailman/rest/tests/test_root.py
@@ -35,7 +35,7 @@ from mailman.config import config
 from mailman.core.system import system
 from mailman.testing.helpers import call_api
 from mailman.testing.layers import RESTLayer
-from urllib2 import HTTPError
+from six.moves.urllib_error import HTTPError
 
 
 
diff --git a/src/mailman/rest/tests/test_users.py b/src/mailman/rest/tests/test_users.py
index 10cc724a3..1936fdc68 100644
--- a/src/mailman/rest/tests/test_users.py
+++ b/src/mailman/rest/tests/test_users.py
@@ -30,15 +30,14 @@ __all__ = [
 import os
 import unittest
 
-from urllib2 import HTTPError
-from zope.component import getUtility
-
 from mailman.app.lifecycle import create_list
 from mailman.config import config
 from mailman.database.transaction import transaction
 from mailman.interfaces.usermanager import IUserManager
 from mailman.testing.helpers import call_api, configuration
 from mailman.testing.layers import RESTLayer
+from six.moves.urllib_error import HTTPError
+from zope.component import getUtility
 
 
 
diff --git a/src/mailman/rest/users.py b/src/mailman/rest/users.py
index cfea36cfa..7e6e70c5a 100644
--- a/src/mailman/rest/users.py
+++ b/src/mailman/rest/users.py
@@ -27,6 +27,8 @@ __all__ = [
     ]
 
 
+import six
+
 from passlib.utils import generate_password as generate
 from uuid import UUID
 from zope.component import getUtility
@@ -58,7 +60,7 @@ class PasswordEncrypterGetterSetter(GetterSetter):
 
 
 ATTRIBUTES = dict(
-    display_name=GetterSetter(unicode),
+    display_name=GetterSetter(six.text_type),
     cleartext_password=PasswordEncrypterGetterSetter(),
     )
 
@@ -105,9 +107,9 @@ class AllUsers(_UserBase):
     def on_post(self, request, response):
         """Create a new user."""
         try:
-            validator = Validator(email=unicode,
-                                  display_name=unicode,
-                                  password=unicode,
+            validator = Validator(email=six.text_type,
+                                  display_name=six.text_type,
+                                  password=six.text_type,
                                   _optional=('display_name', 'password'))
             arguments = validator(request)
         except ValueError as error:
@@ -253,7 +255,7 @@ class Login:
         # We do not want to encrypt the plaintext password given in the POST
         # data.  That would hash the password, but we need to have the
         # plaintext in order to pass into passlib.
-        validator = Validator(cleartext_password=GetterSetter(unicode))
+        validator = Validator(cleartext_password=GetterSetter(six.text_type))
         try:
             values = validator(request)
         except ValueError as error:
diff --git a/src/mailman/rest/validator.py b/src/mailman/rest/validator.py
index cbcc5f652..74a8c0be4 100644
--- a/src/mailman/rest/validator.py
+++ b/src/mailman/rest/validator.py
@@ -62,7 +62,7 @@ def subscriber_validator(subscriber):
     try:
         return UUID(int=int(subscriber))
     except ValueError:
-        return unicode(subscriber)
+        return subscriber.decode('utf-8')
 
 
 def language_validator(code):
diff --git a/src/mailman/runners/command.py b/src/mailman/runners/command.py
index 3d91f663a..54ab03687 100644
--- a/src/mailman/runners/command.py
+++ b/src/mailman/runners/command.py
@@ -31,9 +31,9 @@ __all__ = [
 # -owner.
 
 import re
+import six
 import logging
 
-from StringIO import StringIO
 from email.errors import HeaderParseError
 from email.header import decode_header, make_header
 from email.iterators import typed_subpart_iterator
@@ -76,7 +76,7 @@ class CommandFinder:
         # Extract the subject header and do RFC 2047 decoding.
         raw_subject = msg.get('subject', '')
         try:
-            subject = unicode(make_header(decode_header(raw_subject)))
+            subject = make_header(decode_header(raw_subject)).decode('utf-8')
             # Mail commands must be ASCII.
             self.command_lines.append(subject.encode('us-ascii'))
         except (HeaderParseError, UnicodeError, LookupError):
@@ -84,7 +84,7 @@ class CommandFinder:
             # subject is a unicode object, convert it to ASCII ignoring all
             # bogus characters.  Otherwise, there's nothing in the subject
             # that we can use.
-            if isinstance(raw_subject, unicode):
+            if isinstance(raw_subject, six.text_type):
                 safe_subject = raw_subject.encode('us-ascii', 'ignore')
                 self.command_lines.append(safe_subject)
         # Find the first text/plain part of the message.
@@ -100,7 +100,7 @@ class CommandFinder:
             return
         body = part.get_payload(decode=True)
         # text/plain parts better have string payloads.
-        assert isinstance(body, basestring), 'Non-string decoded payload'
+        assert isinstance(body, six.string_types), 'Non-string decoded payload'
         lines = body.splitlines()
         # Use no more lines than specified
         max_lines = int(config.mailman.email_commands_max_lines)
@@ -118,7 +118,7 @@ class CommandFinder:
             # Ensure that all the parts are unicodes.  Since we only accept
             # ASCII commands and arguments, ignore anything else.
             parts = [(part
-                      if isinstance(part, unicode)
+                      if isinstance(part, six.text_type)
                       else part.decode('ascii', 'ignore'))
                      for part in parts]
             yield parts
@@ -130,20 +130,20 @@ class Results:
     """The email command results."""
 
     def __init__(self, charset='us-ascii'):
-        self._output = StringIO()
+        self._output = six.StringIO()
         self.charset = charset
         print(_("""\
 The results of your email command are provided below.
 """), file=self._output)
 
     def write(self, text):
-        if not isinstance(text, unicode):
+        if isinstance(text, bytes):
             text = text.decode(self.charset, 'ignore')
         self._output.write(text)
 
     def __unicode__(self):
         value = self._output.getvalue()
-        assert isinstance(value, unicode), 'Not a unicode: %r' % value
+        assert isinstance(value, six.text_type), 'Not a unicode: %r' % value
         return value
 
 
@@ -231,7 +231,7 @@ class CommandRunner(Runner):
         # Find a charset for the response body.  Try the original message's
         # charset first, then ascii, then latin-1 and finally falling back to
         # utf-8.
-        reply_body = unicode(results)
+        reply_body = results.decode('utf-8')
         for charset in (results.charset, 'us-ascii', 'latin-1'):
             try:
                 reply_body.encode(charset)
diff --git a/src/mailman/runners/digest.py b/src/mailman/runners/digest.py
index 98fe82f39..628a08e0c 100644
--- a/src/mailman/runners/digest.py
+++ b/src/mailman/runners/digest.py
@@ -28,8 +28,6 @@ __all__ = [
 import re
 import logging
 
-# cStringIO doesn't support unicode.
-from StringIO import StringIO
 from copy import deepcopy
 from email.header import Header
 from email.message import Message
@@ -37,8 +35,6 @@ from email.mime.message import MIMEMessage
 from email.mime.multipart import MIMEMultipart
 from email.mime.text import MIMEText
 from email.utils import formatdate, getaddresses, make_msgid
-from urllib2 import URLError
-
 from mailman.config import config
 from mailman.core.i18n import _
 from mailman.core.runner import Runner
@@ -47,6 +43,8 @@ from mailman.interfaces.member import DeliveryMode, DeliveryStatus
 from mailman.utilities.i18n import make
 from mailman.utilities.mailbox import Mailbox
 from mailman.utilities.string import oneline, wrap
+from six.moves import cStringIO as StringIO
+from six.moves.urllib_error import URLError
 
 
 log = logging.getLogger('mailman.error')
diff --git a/src/mailman/runners/nntp.py b/src/mailman/runners/nntp.py
index 493f8d09a..7d9c189cc 100644
--- a/src/mailman/runners/nntp.py
+++ b/src/mailman/runners/nntp.py
@@ -31,11 +31,11 @@ import socket
 import logging
 import nntplib
 
-from cStringIO import StringIO
-
 from mailman.config import config
 from mailman.core.runner import Runner
 from mailman.interfaces.nntp import NewsgroupModeration
+from six.moves import cStringIO as StringIO
+
 
 COMMA = ','
 COMMASPACE = ', '
diff --git a/src/mailman/runners/tests/test_nntp.py b/src/mailman/runners/tests/test_nntp.py
index 3570d1a6f..191dd2657 100644
--- a/src/mailman/runners/tests/test_nntp.py
+++ b/src/mailman/runners/tests/test_nntp.py
@@ -304,7 +304,7 @@ Testing
         # and make some simple checks that the message is what we expected.
         conn_mock.quit.assert_called_once_with()
 
-    @mock.patch('nntplib.NNTP', side_effect=nntplib.error_temp)
+    @mock.patch('nntplib.NNTP', side_effect=nntplib.NNTPTemporaryError)
     def test_connect_with_nntplib_failure(self, class_mock):
         self._nntpq.enqueue(self._msg, {}, listname='test@example.com')
         mark = LogFileMark('mailman.error')
@@ -341,7 +341,7 @@ Testing
         self.assertEqual(messages[0].msgdata['listname'], 'test@example.com')
         self.assertEqual(messages[0].msg['subject'], 'A newsgroup posting')
 
-    @mock.patch('nntplib.NNTP', side_effect=nntplib.error_temp)
+    @mock.patch('nntplib.NNTP', side_effect=nntplib.NNTPTemporaryError)
     def test_connection_never_gets_quit_after_failures(self, class_mock):
         # The NNTP connection doesn't get closed after a unsuccessful
         # connection, since there's nothing to close.
@@ -361,7 +361,7 @@ Testing
         # The NNTP connection does get closed after a unsuccessful post.
         # Add a side-effect to the instance mock's .post() method.
         conn_mock = class_mock()
-        conn_mock.post.side_effect = nntplib.error_temp
+        conn_mock.post.side_effect = nntplib.NNTPTemporaryError
         self._nntpq.enqueue(self._msg, {}, listname='test@example.com')
         self._runner.run()
         # The connection object's post() method was called once with a
diff --git a/src/mailman/testing/helpers.py b/src/mailman/testing/helpers.py
index b0fe14a0d..1de0e98cf 100644
--- a/src/mailman/testing/helpers.py
+++ b/src/mailman/testing/helpers.py
@@ -59,8 +59,8 @@ from contextlib import contextmanager
 from email import message_from_string
 from httplib2 import Http
 from lazr.config import as_timedelta
-from urllib import urlencode
-from urllib2 import HTTPError
+from six.moves.urllib_error import HTTPError
+from six.moves.urllib_parse import urlencode
 from zope import event
 from zope.component import getUtility
 
@@ -342,7 +342,7 @@ def call_api(url, data=None, method=None, username=None, password=None):
     if len(content) == 0:
         return None, response
     # XXX Workaround http://bugs.python.org/issue10038
-    content = unicode(content)
+    content = content.decode('utf-8')
     return json.loads(content), response
 
 
@@ -506,9 +506,8 @@ def specialized_message_from_string(unicode_text):
     """
     # This mimic what Switchboard.dequeue() does when parsing a message from
     # text into a Message instance.
-    text = unicode_text.encode('ascii')
-    original_size = len(text)
-    message = message_from_string(text, Message)
+    original_size = len(unicode_text)
+    message = message_from_string(unicode_text, Message)
     message.original_size = original_size
     return message
 
diff --git a/src/mailman/testing/layers.py b/src/mailman/testing/layers.py
index 74ad99dc8..8ec6c307f 100644
--- a/src/mailman/testing/layers.py
+++ b/src/mailman/testing/layers.py
@@ -46,7 +46,7 @@ import datetime
 import tempfile
 
 from lazr.config import as_boolean
-from pkg_resources import resource_string
+from pkg_resources import resource_string as resource_bytes
 from textwrap import dedent
 from zope.component import getUtility
 
@@ -132,7 +132,8 @@ class ConfigLayer(MockAndMonkeyLayer):
         configuration: {1}
         """.format(cls.var_dir, postfix_cfg))
         # Read the testing config and push it.
-        test_config += resource_string('mailman.testing', 'testing.cfg')
+        more = resource_bytes('mailman.testing', 'testing.cfg')
+        test_config += more.decode('utf-8')
         config.create_paths = True
         config.push('test config', test_config)
         # Initialize everything else.
diff --git a/src/mailman/testing/mta.py b/src/mailman/testing/mta.py
index 875647485..234540e98 100644
--- a/src/mailman/testing/mta.py
+++ b/src/mailman/testing/mta.py
@@ -27,10 +27,9 @@ __all__ = [
 
 import logging
 
-from Queue import Empty, Queue
-
 from lazr.smtptest.controller import QueueController
 from lazr.smtptest.server import Channel, QueueServer
+from six.moves.queue import Empty, Queue
 from zope.interface import implementer
 
 from mailman.interfaces.mta import IMailTransportAgentLifecycle
diff --git a/src/mailman/utilities/email.py b/src/mailman/utilities/email.py
index 7025ddb89..a15c86fb5 100644
--- a/src/mailman/utilities/email.py
+++ b/src/mailman/utilities/email.py
@@ -68,7 +68,7 @@ def add_message_hash(msg):
         message_id = message_id[1:-1]
     else:
         message_id = message_id.strip()
-    digest = sha1(message_id).digest()
+    digest = sha1(message_id.encode('utf-8')).digest()
     message_id_hash = b32encode(digest)
     del msg['x-message-id-hash']
     msg['X-Message-ID-Hash'] = message_id_hash
diff --git a/src/mailman/utilities/i18n.py b/src/mailman/utilities/i18n.py
index e22bd6c18..e9136837f 100644
--- a/src/mailman/utilities/i18n.py
+++ b/src/mailman/utilities/i18n.py
@@ -29,6 +29,7 @@ __all__ = [
 
 
 import os
+import six
 import sys
 import errno
 
@@ -203,7 +204,8 @@ def make(template_file, mlist=None, language=None, wrap=True,
         template = _(fp.read()[:-1])
     finally:
         fp.close()
-    assert isinstance(template, unicode), 'Translated template is not unicode'
+    assert isinstance(template, six.text_type), (
+        'Translated template is not unicode')
     text = expand(template, kw)
     if wrap:
         return wrap_text(text)
diff --git a/src/mailman/utilities/importer.py b/src/mailman/utilities/importer.py
index cc8a0cf44..5cc52fef7 100644
--- a/src/mailman/utilities/importer.py
+++ b/src/mailman/utilities/importer.py
@@ -48,7 +48,7 @@ from mailman.interfaces.nntp import NewsgroupModeration
 from mailman.interfaces.usermanager import IUserManager
 from mailman.utilities.filesystem import makedirs
 from mailman.utilities.i18n import search
-from urllib2 import URLError
+from six.moves.urllib_error import URLError
 from zope.component import getUtility
 
 
diff --git a/src/mailman/utilities/tests/test_import.py b/src/mailman/utilities/tests/test_import.py
index 42608ae45..de40a3ca1 100644
--- a/src/mailman/utilities/tests/test_import.py
+++ b/src/mailman/utilities/tests/test_import.py
@@ -27,14 +27,14 @@ __all__ = [
 
 
 import os
+import six
 import mock
-import cPickle
 import unittest
 
 from datetime import timedelta, datetime
 from enum import Enum
 from pkg_resources import resource_filename
-from sqlalchemy.exc import IntegrityError
+from six.moves.cPickle import load
 from zope.component import getUtility
 
 from mailman.app.lifecycle import create_list
@@ -78,7 +78,7 @@ class TestBasicImport(unittest.TestCase):
         self._mlist = create_list('blank@example.com')
         pickle_file = resource_filename('mailman.testing', 'config.pck')
         with open(pickle_file) as fp:
-            self._pckdict = cPickle.load(fp)
+            self._pckdict = load(fp)
 
     def _import(self):
         import_config_pck(self._mlist, self._pckdict)
@@ -188,7 +188,7 @@ class TestBasicImport(unittest.TestCase):
         # moderator_password must not be unicode
         self._pckdict[b'mod_password'] = b'TESTVALUE'
         self._import()
-        self.assertFalse(isinstance(self._mlist.moderator_password, unicode))
+        self.assertNotIsInstance(self._mlist.moderator_password, six.text_type)
         self.assertEqual(self._mlist.moderator_password, b'TESTVALUE')
 
     def test_newsgroup_moderation(self):
@@ -263,9 +263,10 @@ class TestBasicImport(unittest.TestCase):
         # Suppress warning messages in test output.
         with mock.patch('sys.stderr'):
             self._import()
-        self.assertEqual(self._mlist.info,
-                         unicode(self._pckdict[b'info'], 'ascii', 'replace'),
-                         "We don't fall back to replacing non-ascii chars")
+        self.assertEqual(
+            self._mlist.info,
+            self._pckdict[b'info'].decode('ascii', 'replace'),
+            "We don't fall back to replacing non-ascii chars")
 
     def test_preferred_language(self):
         self._pckdict[b'preferred_language'] = b'ja'