port just enough of twisted.mail to support running the test setUps

src/twisted/mail/mail.py

@@ -431,7 +431,7 @@ def lineReceived(self, line):
         @type line: L{bytes}
         @param line: A received line.
         """
-        self.fp.write(line + "\n")
+        self.fp.write(line + b"\n")
 
     def eomReceived(self):
         """

src/twisted/mail/maildir.py

@@ -7,18 +7,14 @@
 Maildir-style mailbox support.
 """
 
+import io
 import os
 import stat
 import socket
 from hashlib import md5
 
 from zope.interface import implementer
 
-try:
-    import cStringIO as StringIO
-except ImportError:
-    import StringIO
-
 from twisted.mail import pop3
 from twisted.mail import smtp
 from twisted.protocols import basic
@@ -28,6 +24,7 @@
 from twisted.internet import interfaces, defer, reactor
 from twisted.cred import portal, credentials, checkers
 from twisted.cred.error import UnauthorizedLogin
+from typing import IO
 
 INTERNAL_ERROR = """\
 From: Twisted.mail Internals
@@ -94,6 +91,7 @@ def initializeMaildir(dir):
     @type dir: L{bytes}
     @param dir: The path name for a user directory.
     """
+    dir = os.fsdecode(dir)
     if not os.path.isdir(dir):
         os.mkdir(dir, 0o700)
         for subdir in ["new", "cur", "tmp", ".Trash"]:
@@ -358,7 +356,7 @@ def __init__(self, mbox, msg):
         self.defer = defer.Deferred()
         self.openCall = None
         if not hasattr(msg, "read"):
-            msg = StringIO.StringIO(msg)
+            msg = io.BytesIO(msg)
         self.msg = msg
 
     def startUp(self):
@@ -687,20 +685,20 @@ def listMessages(self, i=None):
             return 0
         return len(self.msgs[i])
 
-    def getMessage(self, i):
+    def getMessage(self, i: int) -> IO[bytes]:
         """
         Return an in-memory file-like object with the contents of a message.
 
         @type i: L{int}
         @param i: The 0-based index of a message.
 
-        @rtype: L{StringIO <cStringIO.StringIO>}
+        @rtype: L{IO[bytes]}
         @return: An in-memory file-like object containing the message.
 
         @raise IndexError: When the index does not correspond to a message in
             the mailbox.
         """
-        return StringIO.StringIO(self.msgs[i])
+        return io.BytesIO(self.msgs[i])
 
     def getUidl(self, i):
         """
@@ -778,8 +776,9 @@ def __init__(self, service, root, postmaster=0):
             should be forwarded to the postmaster (C{True}) or
             bounced (C{False}).
         """
+        root = os.fsencode(root)
         AbstractMaildirDomain.__init__(self, service, root)
-        dbm = os.path.join(root, "passwd")
+        dbm = os.path.join(root, b"passwd")
         if not os.path.exists(dbm):
             os.makedirs(dbm)
         self.dbm = dirdbm.open(dbm)
@@ -801,7 +800,11 @@ def userDirectory(self, name):
             if not self.postmaster:
                 return None
             name = "postmaster"
-        dir = os.path.join(self.root, name)
+        try:
+            dir = os.path.join(self.root, name)
+        except Exception:
+            breakpoint()
+            raise
         if not os.path.exists(dir):
             initializeMaildir(dir)
         return dir

src/twisted/mail/relay.py

@@ -83,7 +83,7 @@ def loadMessages(self, messagePaths):
         self.messages = []
         self.names = []
         for message in messagePaths:
-            with open(message + "-H") as fp:
+            with open(message + "-H", "rb") as fp:
                 messageContents = pickle.load(fp)
             fp = open(message + "-D")
             messageContents.append(fp)