The title says it all. Ideally (!), changing .hgignore should be enough to fix this issue.
(NB: I have only tested the default branch)

======================================================================
FAIL: test_byte_message_rfc822_only (test_email.TestMessageAPI)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\t\cp\lib\test\test_email\test_email.py", line 189, in test_byte_messa
ge_rfc822_only
    self.assertEqual(out.getvalue(), msgdata)
AssertionError: Lists differ: ["b'Return-Path: <sender@examp... != ["b'Return-Pa
th: <sender@examp...

First differing element 0:
b'Return-Path: <sender@example.net>\n'
b'Return-Path: <sender@example.net>\r\n'

- ["b'Return-Path: <sender@example.net>\\n'",
+ ["b'Return-Path: <sender@example.net>\\r\\n'",
?                                        +++

-  "b'Delivery-Date: Mon, 08 Feb 2010 14:05:16 +0100\\n'",
+  "b'Delivery-Date: Mon, 08 Feb 2010 14:05:16 +0100\\r\\n'",
?                                                     +++

-  "b'Received: from example.org (example.org [64.5.53.58])\\n'",
+  "b'Received: from example.org (example.org [64.5.53.58])\\r\\n'",
?                                                            +++

-  "b'    by example.net (node=mxbap2) with ESMTP (Nemesis)\\n'",
+  "b'    by example.net (node=mxbap2) with ESMTP (Nemesis)\\r\\n'",
?                                                            +++

-  "b'    id UNIQUE for someone@example.com; Mon, 08 Feb 2010 14:05:16 +0100\\n'
",
+  "b'    id UNIQUE for someone@example.com; Mon, 08 Feb 2010 14:05:16 +0100\\r\
\n'",
?                                                                             ++
+

-  "b'Date: Mon, 01 Feb 2010 12:21:16 +0100\\n'",
+  "b'Date: Mon, 01 Feb 2010 12:21:16 +0100\\r\\n'",
?                                            +++

-  'b\'From: "Sender" <sender@example.net>\\n\'',
+  'b\'From: "Sender" <sender@example.net>\\r\\n\'',
?                                           +++

-  "b'To: <someone@example.com>\\n'",
+  "b'To: <someone@example.com>\\r\\n'",
?                                +++

-  "b'Subject: GroupwiseForwardingTest\\n'",
+  "b'Subject: GroupwiseForwardingTest\\r\\n'",
?                                       +++

-  "b'Mime-Version: 1.0\\n'",
+  "b'Mime-Version: 1.0\\r\\n'",
?                      +++

-  "b'Content-Type: message/rfc822\\n'",
+  "b'Content-Type: message/rfc822\\r\\n'",
?                                   +++

-  "b'\\n'",
+  "b'\\r\\n'",
?     +++

   "b'Return-path: <sender@example.net>\\r\\n'",
   "b'Message-ID: <4B66B890.4070408@teconcept.de>\\r\\n'",
   "b'Date: Mon, 01 Feb 2010 12:18:40 +0100\\r\\n'",
   'b\'From: "Dr. Sender" <sender@example.net>\\r\\n\'',
   "b'MIME-Version: 1.0\\r\\n'",
   'b\'To: "Recipient" <recipient@example.com>\\r\\n\'',
   "b'Subject: GroupwiseForwardingTest\\r\\n'",
   "b'Content-Type: text/plain; charset=ISO-8859-15\\r\\n'",
   "b'Content-Transfer-Encoding: 7bit\\r\\n'",
   "b'\\r\\n'",
   "b'Testing email forwarding with Groupwise 1.2.2010\\r\\n'"]

======================================================================
FAIL: test_flatten_linesep_overrides_policy (test_email.TestParsers)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\t\cp\lib\test\test_email\test_email.py", line 3074, in test_flatten_l
inesep_overrides_policy
    self.assertEqual(s.getvalue(), text)
AssertionError: 'Return-Path: <aperson@dom.ain>\nReceived: by mail.dom.ain (Post
fix, from userid [truncated]... != 'Return-Path: <aperson@dom.ain>\r\nReceived:
by mail.dom.ain (Postfix, from user [truncated]...
- Return-Path: <aperson@dom.ain>
+ Return-Path: <aperson@dom.ain>
?                               +
- Received: by mail.dom.ain (Postfix, from userid 889)
+ Received: by mail.dom.ain (Postfix, from userid 889)
?                                                     +
-       id B9D0AD35DB; Tue,  4 Jun 2002 21:46:59 -0400 (EDT)
+       id B9D0AD35DB; Tue,  4 Jun 2002 21:46:59 -0400 (EDT)
?                                                           +
- Message-ID: <15613.28051.707126.569693@dom.ain>
+ Message-ID: <15613.28051.707126.569693@dom.ain>
?                                                +
- Date: Tue, 4 Jun 2002 21:46:59 -0400
+ Date: Tue, 4 Jun 2002 21:46:59 -0400
?                                     +
- MIME-Version: 1.0
+ MIME-Version: 1.0
?                  +
- Content-Type: text/plain; charset=us-ascii
+ Content-Type: text/plain; charset=us-ascii
?                                           +
- Content-Transfer-Encoding: 7bit
+ Content-Transfer-Encoding: 7bit
?                                +
- Subject: bug demonstration
+ Subject: bug demonstration
?                           +
-       123456789112345678921234567893123456789412345678951234567896123456789712
34567898112345678911234567892123456789112345678911234567892123456789
+       123456789112345678921234567893123456789412345678951234567896123456789712
34567898112345678911234567892123456789112345678911234567892123456789
?
                                                                    +
-       more text
+       more text
?                +
- From: aperson@dom.ain (Anne P. Erson)
+ From: aperson@dom.ain (Anne P. Erson)
?                                      +
- To: bperson@dom.ain (Barney P. Erson)
+ To: bperson@dom.ain (Barney P. Erson)
?                                      +
-
+
  test


----------------------------------------------------------------------
Ran 502 tests in 4.438s

FAILED (failures=3, skipped=1)