The following builbot failure is probably related:

http://buildbot.python.org/all/builders/AMD64%20Windows8.1%20Non-Debug%203.x/builds/623/steps/test/logs/stdio

======================================================================
FAIL: test_main (test.test_threadedtempfile.ThreadedTempFileTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "D:\buildarea\3.x.ware-win81-release\build\lib\test\test_threadedtempfile.py", line 58, in test_main
    self.assertEqual(errors, [], msg)
AssertionError: Lists differ: ['Thread-813Traceback (most recent call la[2133 chars]g\n'] != []

First list contains 4 additional elements.
First extra element 0:
'Thread-813Traceback (most recent call last):\n  File "D:\\buildarea\\3.x.ware-win81-release\\build\\lib\\test\\test_threadedtempfile.py", line 38, in run\n    f = tempfile.TemporaryFile("w+b")\n  File "D:\\buildarea\\3.x.ware-win81-release\\build\\lib\\tempfile.py", line 538, in NamedTemporaryFile\n    (fd, name) = _mkstemp_inner(dir, prefix, suffix, flags, output_type)\n  File "D:\\buildarea\\3.x.ware-win81-release\\build\\lib\\tempfile.py", line 246, in _mkstemp_inner\n    name = next(names)\nValueError: generator already executing\n'

Diff is 2461 characters long. Set self.maxDiff to None to see it. : Errors: errors 4 ok 996
Thread-813Traceback (most recent call last):
  File "D:\buildarea\3.x.ware-win81-release\build\lib\test\test_threadedtempfile.py", line 38, in run
    f = tempfile.TemporaryFile("w+b")
  File "D:\buildarea\3.x.ware-win81-release\build\lib\tempfile.py", line 538, in NamedTemporaryFile
    (fd, name) = _mkstemp_inner(dir, prefix, suffix, flags, output_type)
  File "D:\buildarea\3.x.ware-win81-release\build\lib\tempfile.py", line 246, in _mkstemp_inner
    name = next(names)
ValueError: generator already executing

Thread-814Traceback (most recent call last):
  File "D:\buildarea\3.x.ware-win81-release\build\lib\test\test_threadedtempfile.py", line 38, in run
    f = tempfile.TemporaryFile("w+b")
  File "D:\buildarea\3.x.ware-win81-release\build\lib\tempfile.py", line 538, in NamedTemporaryFile
    (fd, name) = _mkstemp_inner(dir, prefix, suffix, flags, output_type)
  File "D:\buildarea\3.x.ware-win81-release\build\lib\tempfile.py", line 246, in _mkstemp_inner
    name = next(names)
ValueError: generator already executing

Thread-819Traceback (most recent call last):
  File "D:\buildarea\3.x.ware-win81-release\build\lib\test\test_threadedtempfile.py", line 38, in run
    f = tempfile.TemporaryFile("w+b")
  File "D:\buildarea\3.x.ware-win81-release\build\lib\tempfile.py", line 538, in NamedTemporaryFile
    (fd, name) = _mkstemp_inner(dir, prefix, suffix, flags, output_type)
  File "D:\buildarea\3.x.ware-win81-release\build\lib\tempfile.py", line 246, in _mkstemp_inner
    name = next(names)
ValueError: generator already executing

Thread-823Traceback (most recent call last):
  File "D:\buildarea\3.x.ware-win81-release\build\lib\test\test_threadedtempfile.py", line 38, in run
    f = tempfile.TemporaryFile("w+b")
  File "D:\buildarea\3.x.ware-win81-release\build\lib\tempfile.py", line 538, in NamedTemporaryFile
    (fd, name) = _mkstemp_inner(dir, prefix, suffix, flags, output_type)
  File "D:\buildarea\3.x.ware-win81-release\build\lib\tempfile.py", line 246, in _mkstemp_inner
    name = next(names)
ValueError: generator already executing