Maildir.newMessage returns a MaildirMessageWriter with a file handl…

…e opened

in text mode, see
https://github.com/zopefoundation/zope.sendmail/blob/2ee8b0a454ff484335e6b65b9d46a695309a2b2f/src/zope/sendmail/maildir.py#L110
(mode is 'w' not 'wb')

But `MaildirMessageWriter.write` writes bytes to this file handle, see
https://github.com/zopefoundation/zope.sendmail/blob/2ee8b0a454ff484335e6b65b9d46a695309a2b2f/src/zope/sendmail/maildir.py#L131-L132

This commit changes the implementation to use bytes for Python 3.

The change is necessary to get the tests in zopefoundation/Products.MailHost#15 green.

Closes #23. (Which had a different implementation.)

CHANGES.rst

@@ -5,7 +5,7 @@
 4.2.2 (unreleased)
 ==================
 
-- Nothing changed yet.
+- Fix text/bytes issue in MailDir for Python 3.
 
 
 4.2.1 (2019-02-07)

src/zope/sendmail/maildir.py

@@ -107,7 +107,7 @@ def newMessage(self):
                 time.sleep(0.1)
             else:
                 break
-        return MaildirMessageWriter(os.fdopen(fd, 'w'), filename,
+        return MaildirMessageWriter(os.fdopen(fd, 'wb'), filename,
                                     join(subdir_new, unique))
 
 

src/zope/sendmail/tests/test_maildir.py

@@ -146,7 +146,7 @@ def fdopen(self, fd, mode='r'):
         except KeyError:  # pragma: no cover
             raise AssertionError('os.fdopen() called with an unknown'
                                  ' file descriptor')
-        assert mode == 'w'
+        assert mode == 'wb'
         assert flags & os.O_WRONLY
         assert not flags & os.O_RDWR
         return FakeFile(filename, mode)