Correct test_mailbox on win32: since the test sets a custom 'colon' attribute
to the main mailbox, copy it to secondary mailbox instances.
diff --git a/Lib/test/test_mailbox.py b/Lib/test/test_mailbox.py
index ff214ce..9206dc4 100644
--- a/Lib/test/test_mailbox.py
+++ b/Lib/test/test_mailbox.py
@@ -520,6 +520,7 @@
         class FakeMessage(mailbox.MaildirMessage):
             pass
         box = mailbox.Maildir(self._path, factory=FakeMessage)
+        box.colon = self._box.colon
         msg2 = box.get_message(key)
         self.assert_(isinstance(msg2, FakeMessage))