Hum, _Py_fstat() is not used correctly in _io.FilIO: it uses errno instead of GetLastError() to raise the OSError. It's too hard to use the new _Py_fstat() function directly, I modified it to raise directly the exception. So the caller doesn't have to use #ifdef MS_WINDOWS to raise the exception correctly.

I added _Py_fstat_noraise() when it's not possible to use an exception.

http://buildbot.python.org/all/builders/AMD64%20Windows7%20SP1%203.x/builds/5978/steps/test/logs/stdio

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FAIL: test_fdopen (test.test_os.TestInvalidFD)
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Traceback (most recent call last):
  File "C:\buildbot.python.org\3.x.kloth-win64\build\lib\test\test_os.py", line 1418, in check
    f(support.make_bad_fd(), *args)
  File "C:\buildbot.python.org\3.x.kloth-win64\build\lib\os.py", line 1028, in fdopen
    return io.open(fd, *args, **kwargs)
OSError: [Errno 0] Error

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\buildbot.python.org\3.x.kloth-win64\build\lib\test\test_os.py", line 1411, in helper
    self.check(getattr(os, f))
  File "C:\buildbot.python.org\3.x.kloth-win64\build\lib\test\test_os.py", line 1420, in check
    self.assertEqual(e.errno, errno.EBADF)
AssertionError: 0 != 9