This issue is not fixed on windows yet. (test_leaking_fds_on_error fails)
I think attached patch will fix this.
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ERROR: test_writes_before_communicate (__main__.ProcessTestCase)
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Traceback (most recent call last):
File "test_subprocess.py", line 398, in test_writes_before_communicate
File "e:\python-dev\py3k\lib\subprocess.py", line 632, in __init__
File "e:\python-dev\py3k\lib\subprocess.py", line 746, in _get_handles
IOError: [Errno 24] Too many open files