For some reason sys.stdin may be None on Windows, and makes test_multiprocessing fail.

Since we are closing the fileno anyway, the best is to skip this part.

Now test_multiprocessing should pass on Windows.

Lib/multiprocessing/process.py

@@ -219,6 +219,7 @@ class Process(object):
         try:
             self._children = set()
             self._counter = itertools.count(1)
+            if sys.stdin is not None:
                 try:
                     os.close(sys.stdin.fileno())
                 except (OSError, ValueError):