[ 62/359] test_multiprocessing
Warning -- threading._dangling was modified by test_multiprocessing
Warning -- multiprocessing.process._dangling was modified by test_multiprocessing
test test_multiprocessing crashed -- Traceback (most recent call last):
  File "/var/lib/buildslave/3.x.murray-gentoo/build/Lib/test/regrtest.py", line 1163, in runtest_inner
    indirect_test()
  File "/var/lib/buildslave/3.x.murray-gentoo/build/Lib/test/test_multiprocessing.py", line 2349, in test_main
    ManagerMixin.pool = ManagerMixin.manager.Pool(4)
  File "/var/lib/buildslave/3.x.murray-gentoo/build/Lib/multiprocessing/managers.py", line 670, in temp
    token, exp = self._create(typeid, *args, **kwds)
  File "/var/lib/buildslave/3.x.murray-gentoo/build/Lib/multiprocessing/managers.py", line 568, in _create
    conn = self._Client(self._address, authkey=self._authkey)
  File "/var/lib/buildslave/3.x.murray-gentoo/build/Lib/multiprocessing/connection.py", line 507, in Client
    answer_challenge(c, authkey)
  File "/var/lib/buildslave/3.x.murray-gentoo/build/Lib/multiprocessing/connection.py", line 734, in answer_challenge
    message = connection.recv_bytes(256)         # reject large message
  File "/var/lib/buildslave/3.x.murray-gentoo/build/Lib/multiprocessing/connection.py", line 243, in recv_bytes
    self._bad_message_length()
  File "/var/lib/buildslave/3.x.murray-gentoo/build/Lib/multiprocessing/connection.py", line 175, in _bad_message_length
    raise IOError("bad message length")
IOError: bad message length

http://www.python.org/dev/buildbot/all/builders/x86%20Gentoo%203.x/builds/828/steps/test/logs/stdio

See also issue #13063.

This is a really weird error. At this point, the child is waiting for a challenge from the parent, and the challenge is something like 32 bytes long:

    message = os.urandom(MESSAGE_LENGTH)
    connection.send_bytes(CHALLENGE + message)

So, this can only mean, IMO, that someone else than the parent (another process?) is writing on the socket...

@antoine: can you try to add more debug messages?

Sporadic failure, I don't know if it was reproduced recently, and the issue has no activity since more than 6 months => I'm closing the issue.