16 files changed, 46 insertions, 82 deletions

diff --git a/src/mailman/app/tests/test_subscriptions.py b/src/mailman/app/tests/test_subscriptions.py
index 1139591de..11512bcfe 100644
--- a/src/mailman/app/tests/test_subscriptions.py
+++ b/src/mailman/app/tests/test_subscriptions.py
@@ -19,6 +19,7 @@
 
 import unittest
 
+from contextlib import suppress
 from mailman.app.lifecycle import create_list
 from mailman.app.subscriptions import SubscriptionWorkflow
 from mailman.interfaces.bans import IBanManager
@@ -57,10 +58,8 @@ class TestSubscriptionWorkflow(unittest.TestCase):
         # some data associated with it.
         anne = self._user_manager.create_address(self._anne)
         workflow = SubscriptionWorkflow(self._mlist, anne)
-        try:
+        with suppress(StopIteration):
             workflow.run_thru('send_confirmation')
-        except StopIteration:
-            pass
         self.assertIsNotNone(workflow.token)
         pendable = getUtility(IPendings).confirm(workflow.token, expunge=False)
         self.assertEqual(pendable['list_id'], 'test.example.com')
diff --git a/src/mailman/bin/docs/master.rst b/src/mailman/bin/docs/master.rst
index 5a3a94da6..c9bd60f13 100644
--- a/src/mailman/bin/docs/master.rst
+++ b/src/mailman/bin/docs/master.rst
@@ -41,13 +41,8 @@ runner processes.
 None of the children are running now.
 
     >>> import errno
+    >>> from contextlib import suppress
     >>> for pid in master.runner_pids:
-    ...     try:
+    ...     with suppress(ProcessLookupError):
     ...         os.kill(pid, 0)
     ...         print('Process did not exit:', pid)
-    ...     except OSError as error:
-    ...         if error.errno == errno.ESRCH:
-    ...             # The child process exited.
-    ...             pass
-    ...         else:
-    ...             raise
diff --git a/src/mailman/commands/cli_withlist.py b/src/mailman/commands/cli_withlist.py
index 79dc3b966..127308a05 100644
--- a/src/mailman/commands/cli_withlist.py
+++ b/src/mailman/commands/cli_withlist.py
@@ -20,7 +20,7 @@
 import re
 import sys
 
-from contextlib import ExitStack
+from contextlib import ExitStack, suppress
 from functools import partial
 from lazr.config import as_boolean
 from mailman import public
@@ -222,10 +222,8 @@ class Withlist:
                         }
                     history_file = Template(
                         history_file_template).safe_substitute(substitutions)
-                    try:
+                    with suppress(FileNotFoundError):
                         readline.read_history_file(history_file)
-                    except FileNotFoundError:
-                        pass
                     resources.callback(
                         readline.write_history_file,
                         history_file)
diff --git a/src/mailman/commands/tests/test_control.py b/src/mailman/commands/tests/test_control.py
index 26d921cd7..7377c4666 100644
--- a/src/mailman/commands/tests/test_control.py
+++ b/src/mailman/commands/tests/test_control.py
@@ -56,22 +56,12 @@ def find_master():
     until = timedelta(seconds=10) + datetime.now()
     while datetime.now() < until:
         time.sleep(0.1)
-        try:
+        with suppress(FileNotFoundError, ValueError, ProcessLookupError):
             with open(config.PID_FILE) as fp:
                 pid = int(fp.read().strip())
                 os.kill(pid, 0)
-        except IOError as error:
-            if error.errno != errno.ENOENT:
-                raise
-        except ValueError:
-            pass
-        except OSError as error:
-            if error.errno != errno.ESRCH:
-                raise
-        else:
-            return pid
-    else:
-        return None
+                return pid
+    return None
 
 
 class FakeArgs:
diff --git a/src/mailman/core/runner.py b/src/mailman/core/runner.py
index 4c9c59464..d193a1082 100644
--- a/src/mailman/core/runner.py
+++ b/src/mailman/core/runner.py
@@ -22,6 +22,7 @@ import signal
 import logging
 import traceback
 
+from contextlib import suppress
 from io import StringIO
 from lazr.config import as_boolean, as_timedelta
 from mailman import public
@@ -112,7 +113,7 @@ class Runner:
     def run(self):
         """See `IRunner`."""
         # Start the main loop for this runner.
-        try:
+        with suppress(KeyboardInterrupt):
             while True:
                 # Once through the loop that processes all the files in the
                 # queue directory.
@@ -126,10 +127,7 @@ class Runner:
                 # pass it the file count so it can decide whether to do more
                 # work now or not.
                 self._snooze(filecnt)
-        except KeyboardInterrupt:
-            pass
-        finally:
-            self._clean_up()
+        self._clean_up()
 
     def _one_iteration(self):
         """See `IRunner`."""
diff --git a/src/mailman/database/tests/test_factory.py b/src/mailman/database/tests/test_factory.py
index d8593cc76..74b45e43a 100644
--- a/src/mailman/database/tests/test_factory.py
+++ b/src/mailman/database/tests/test_factory.py
@@ -20,6 +20,7 @@
 import unittest
 import alembic.command
 
+from contextlib import suppress
 from mailman.config import config
 from mailman.database.alembic import alembic_cfg
 from mailman.database.factory import LAST_STORM_SCHEMA_VERSION, SchemaManager
@@ -87,12 +88,10 @@ class TestSchemaManager(unittest.TestCase):
             version = Model.metadata.tables['version']
             version.drop(config.db.engine, checkfirst=True)
             Model.metadata.remove(version)
-        try:
+        # If it's nonexistent, PostgreSQL raises a ProgrammingError, while
+        # SQLite raises an OperationalError.
+        with suppress(ProgrammingError, OperationalError):
             Index('ix_user_user_id').drop(bind=config.db.engine)
-        except (ProgrammingError, OperationalError):
-            # Nonexistent.  PostgreSQL raises a ProgrammingError, while SQLite
-            # raises an OperationalError.
-            pass
         config.db.commit()
 
     def test_current_database(self):
diff --git a/src/mailman/handlers/mime_delete.py b/src/mailman/handlers/mime_delete.py
index 267cb227a..b88c40b0c 100644
--- a/src/mailman/handlers/mime_delete.py
+++ b/src/mailman/handlers/mime_delete.py
@@ -30,7 +30,7 @@ import logging
 import tempfile
 import subprocess
 
-from contextlib import ExitStack
+from contextlib import ExitStack, suppress
 from email.iterators import typed_subpart_iterator
 from email.mime.message import MIMEMessage
 from email.mime.text import MIMEText
@@ -220,11 +220,9 @@ def collapse_multipart_alternatives(msg):
     newpayload = []
     for subpart in msg.get_payload():
         if subpart.get_content_type() == 'multipart/alternative':
-            try:
+            with suppress(IndexError):
                 firstalt = subpart.get_payload(0)
                 newpayload.append(firstalt)
-            except IndexError:
-                pass
         else:
             newpayload.append(subpart)
     msg.set_payload(newpayload)
diff --git a/src/mailman/handlers/subject_prefix.py b/src/mailman/handlers/subject_prefix.py
index 8a9da8b42..ff728d92e 100644
--- a/src/mailman/handlers/subject_prefix.py
+++ b/src/mailman/handlers/subject_prefix.py
@@ -19,7 +19,8 @@
 
 import re
 
-from email.header import Header, make_header, decode_header
+from contextlib import suppress
+from email.header import Header, decode_header, make_header
 from mailman import public
 from mailman.core.i18n import _
 from mailman.interfaces.handler import IHandler
@@ -163,10 +164,8 @@ class SubjectPrefix:
             # subject.  Also, force new style.
             prefix_pattern = p.sub(r'\s*\d+\s*', prefix_pattern)
         # Substitute %d in prefix with post_id
-        try:
+        with suppress(TypeError):
             prefix = prefix % mlist.post_id
-        except TypeError:
-            pass
         for handler in (ascii_header,
                         all_same_charset,
                         mixed_charsets,
diff --git a/src/mailman/model/messagestore.py b/src/mailman/model/messagestore.py
index b17118330..8949c56c6 100644
--- a/src/mailman/model/messagestore.py
+++ b/src/mailman/model/messagestore.py
@@ -27,7 +27,7 @@ from mailman.database.transaction import dbconnection
 from mailman.interfaces.messages import IMessageStore
 from mailman.model.message import Message
 from mailman.utilities.email import add_message_hash
-from mailman.utilities.filesystem import makedirs
+from mailman.utilities.filesystem import makedirs, safe_remove
 from zope.interface import implementer
 
 
@@ -123,8 +123,5 @@ class MessageStore:
             path = os.path.join(config.MESSAGES_DIR, row.path)
             # It's possible that a race condition caused the file system path
             # to already be deleted.
-            try:
-                os.remove(path)
-            except FileNotFoundError:
-                pass
+            safe_remove(path)
             store.delete(row)
diff --git a/src/mailman/rules/implicit_dest.py b/src/mailman/rules/implicit_dest.py
index 621ad3e22..c0e116d1c 100644
--- a/src/mailman/rules/implicit_dest.py
+++ b/src/mailman/rules/implicit_dest.py
@@ -19,6 +19,7 @@
 
 import re
 
+from contextlib import suppress
 from email.utils import getaddresses
 from mailman import public
 from mailman.core.i18n import _
@@ -83,10 +84,8 @@ class ImplicitDestination:
                 except re.error:
                     # The pattern is a malformed regular expression.  Try
                     # matching again with the pattern escaped.
-                    try:
+                    with suppress(re.error):
                         if re.match(escaped, recipient, re.IGNORECASE):
                             return False
-                    except re.error:
-                        pass
         # Nothing matched.
         return True
diff --git a/src/mailman/runners/command.py b/src/mailman/runners/command.py
index 13d52ce75..00f6f416b 100644
--- a/src/mailman/runners/command.py
+++ b/src/mailman/runners/command.py
@@ -25,6 +25,7 @@
 import re
 import logging
 
+from contextlib import suppress
 from email.errors import HeaderParseError
 from email.header import decode_header, make_header
 from email.iterators import typed_subpart_iterator
@@ -224,11 +225,9 @@ class CommandRunner(Runner):
         # utf-8.
         reply_body = str(results)
         for charset in (results.charset, 'us-ascii', 'latin-1'):
-            try:
+            with suppress(UnicodeError):
                 reply_body.encode(charset)
                 break
-            except UnicodeError:
-                pass
         else:
             charset = 'utf-8'
         reply.set_payload(reply_body, charset=charset)
diff --git a/src/mailman/runners/incoming.py b/src/mailman/runners/incoming.py
index dd9254194..62b12dab1 100644
--- a/src/mailman/runners/incoming.py
+++ b/src/mailman/runners/incoming.py
@@ -26,6 +26,7 @@ prepared for delivery.  Rejections, discards, and holds are processed
 immediately.
 """
 
+from contextlib import suppress
 from mailman import public
 from mailman.core.chains import process
 from mailman.core.runner import Runner
@@ -48,10 +49,8 @@ class IncomingRunner(Runner):
         user_manager = getUtility(IUserManager)
         with transaction():
             for sender in msg.senders:
-                try:
+                with suppress(ExistingAddressError):
                     user_manager.create_address(sender)
-                except ExistingAddressError:
-                    pass
         # Process the message through the mailing list's start chain.
         start_chain = (mlist.owner_chain
                        if msgdata.get('to_owner', False)
diff --git a/src/mailman/testing/helpers.py b/src/mailman/testing/helpers.py
index 3edd66479..a87dd58ec 100644
--- a/src/mailman/testing/helpers.py
+++ b/src/mailman/testing/helpers.py
@@ -31,7 +31,7 @@ import datetime
 import threading
 
 from base64 import b64encode
-from contextlib import contextmanager
+from contextlib import contextmanager, suppress
 from email import message_from_string
 from httplib2 import Http
 from lazr.config import as_timedelta
@@ -183,14 +183,11 @@ class TestableMaster(Master):
         starting_kids = set(self._kids)
         while starting_kids:
             for pid in self._kids:
-                try:
+                # Ignore the exception which gets raised when the child has
+                # not yet started.
+                with suppress(ProcessLookupError):
                     os.kill(pid, 0)
                     starting_kids.remove(pid)
-                except OSError as error:
-                    if error.errno == errno.ESRCH:
-                        # The child has not yet started.
-                        pass
-                    raise
         # Keeping a copy of all the started child processes for use by the
         # testing environment, even after all have exited.
         self._started_kids = set(self._kids)
diff --git a/src/mailman/utilities/filesystem.py b/src/mailman/utilities/filesystem.py
index e8935b92c..e89f2abb8 100644
--- a/src/mailman/utilities/filesystem.py
+++ b/src/mailman/utilities/filesystem.py
@@ -18,8 +18,8 @@
 """Filesystem utilities."""
 
 import os
-import errno
 
+from contextlib import suppress
 from mailman import public
 
 
@@ -54,18 +54,18 @@ def makedirs(path, mode=0o2775):
     :param mode: The numeric permission mode to use.
     :type mode: int
     """
-    try:
+    with suppress(FileExistsError):
         with umask(0):
             os.makedirs(path, mode)
-    except OSError as error:
-        # Ignore the exceptions if the directory already exists.
-        if error.errno != errno.EEXIST:
-            raise
     # Some systems such as FreeBSD ignore mkdir's mode, so walk the just
     # created directories and try to set the mode, ignoring any OSErrors that
     # occur here.
     for dirpath, dirnames, filenames in os.walk(path):
-        try:
+        with suppress(OSError):
             os.chmod(dirpath, mode)
-        except OSError:
-            pass
+
+
+@public
+def safe_remove(path):
+    with suppress(FileNotFoundError):
+        os.remove(path)
diff --git a/src/mailman/utilities/interact.py b/src/mailman/utilities/interact.py
index 3cc5dddc6..904d1b579 100644
--- a/src/mailman/utilities/interact.py
+++ b/src/mailman/utilities/interact.py
@@ -21,6 +21,7 @@ import os
 import sys
 import code
 
+from contextlib import suppress
 from mailman import public
 
 
@@ -51,10 +52,8 @@ def interact(upframe=True, banner=DEFAULT_BANNER, overrides=None):
         namespace.update(overrides)
     interp = code.InteractiveConsole(namespace)
     # Try to import the readline module, but don't worry if it's unavailable.
-    try:
+    with suppress(ImportError):
         import readline                             # noqa
-    except ImportError:                             # pragma: no cover
-        pass
     # Mimic the real interactive interpreter's loading of any $PYTHONSTARTUP
     # file.  Note that if the startup file is not prepared to be exec'd more
     # than once, this could cause a problem.
diff --git a/src/mailman/utilities/uid.py b/src/mailman/utilities/uid.py
index cef0ebc87..4389bcd92 100644
--- a/src/mailman/utilities/uid.py
+++ b/src/mailman/utilities/uid.py
@@ -27,6 +27,7 @@ import uuid
 import random
 import hashlib
 
+from contextlib import suppress
 from flufl.lock import Lock
 from mailman import public
 from mailman.config import config
@@ -125,11 +126,8 @@ class UIDFactory(_PredictableIDGenerator):
         """
         while True:
             uid = uuid.uuid4()
-            try:
+            with suppress(ValueError):
                 UID.record(uid)
-            except ValueError:
-                pass
-            else:
                 return uid
 
     def _next_predictable_id(self):