Several fixes and cleanups, ostensibly to fix Python 2.6 support.

- email.iterators.body_line_iterator() cannot handle unicodes in Python 2.6,
  because it uses cStringIO.StringIO under the covers, and *that* can't handle
  unicode.  This works fine in Python 2.7, so I override this for the tests
  only under 2.6 (the code itself isn't affected).

- AddressError needs to str() its IAddress attribute explicitly in the
  __str__() method, otherwise under Python 2.6, you'll get unprintable reprs
  in the doctests.  Again, this works correctly in 2.7, but EIBTI, so it can't
  hurt either way.

- EmailError: a new exception, not related to AddressError.  The reason for
  this it to conform to current nomenclature: "address" means an IAddress
  while "email" means a text email address.  So InvalidEmailAddressError
  now derives from EmailError instead of AddressError because it gets passed a
  text email address, and because that is invalid, it never gets turned into
  an IAddress.  The __str__() of this new base exception class does some
  tricky encoding to keep it compatible between Python 2.6 and 2.7.

- UnverifiedAddressError derives from AddressError instead of the more generic
  MailmanError.

- A few random code cleanups are included.

2 files changed, 23 insertions, 14 deletions

diff --git a/src/mailman/interfaces/address.py b/src/mailman/interfaces/address.py
index 6c371e1c0..cf2c50bf4 100644
--- a/src/mailman/interfaces/address.py
+++ b/src/mailman/interfaces/address.py
@@ -17,13 +17,14 @@
 
 """Interface for email address related information."""
 
-from __future__ import absolute_import, unicode_literals
+from __future__ import absolute_import, print_function, unicode_literals
 
 __metaclass__ = type
 __all__ = [
     'AddressAlreadyLinkedError',
     'AddressError',
     'AddressNotLinkedError',
+    'EmailError',
     'ExistingAddressError',
     'IAddress',
     'IEmailValidator',
@@ -37,15 +38,30 @@ from mailman.interfaces.errors import MailmanError
 
 
 
+class EmailError(MailmanError):
+    """A generic text email address-related error occurred."""
+
+    def __init__(self, email):
+        super(EmailError, self).__init__()
+        self.email = email
+
+    def __str__(self):
+        # This is a workaround for Python 2.6 support.  When self.email
+        # contains non-ascii characters, this will cause unprintable output in
+        # doctests.  Python 2.7 can handle it but we haven't dropped support
+        # for 2.6 yet.
+        return self.email.encode('us-ascii', 'backslashreplace')
+
+
 class AddressError(MailmanError):
-    """A general address-related error occurred."""
+    """A generic IAddress-related error occurred."""
 
     def __init__(self, address):
         super(AddressError, self).__init__()
         self.address = address
 
     def __str__(self):
-        return self.address
+        return str(self.address)
 
 
 class ExistingAddressError(AddressError):
@@ -60,7 +76,7 @@ class AddressNotLinkedError(AddressError):
     """The address is not linked to the user."""
 
 
-class InvalidEmailAddressError(AddressError):
+class InvalidEmailAddressError(EmailError):
     """Email address is invalid."""
 
 
diff --git a/src/mailman/interfaces/user.py b/src/mailman/interfaces/user.py
index aba9bcbba..8d0cbfb54 100644
--- a/src/mailman/interfaces/user.py
+++ b/src/mailman/interfaces/user.py
@@ -17,7 +17,7 @@
 
 """Interface describing the basics of a user."""
 
-from __future__ import absolute_import, unicode_literals
+from __future__ import absolute_import, print_function, unicode_literals
 
 __metaclass__ = type
 __all__ = [
@@ -28,20 +28,13 @@ __all__ = [
 
 from zope.interface import Interface, Attribute
 
-from mailman.interfaces.errors import MailmanError
+from mailman.interfaces.address import AddressError
 
 
 
-class UnverifiedAddressError(MailmanError):
+class UnverifiedAddressError(AddressError):
     """Unverified address cannot be used as a user's preferred address."""
 
-    def __init__(self, address):
-        super(UnverifiedAddressError, self).__init__()
-        self.address = address
-
-    def __str__(self):
-        return self.address
-
 
 
 class IUser(Interface):