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Python 2.7 doesn't seem to be affected by this issue. Extract of Popen.__init__:
 try:
 self._execute_child(args, executable, preexec_fn, close_fds,
 cwd, env, universal_newlines,
 startupinfo, creationflags, shell, to_close,
 p2cread, p2cwrite,
 c2pread, c2pwrite,
 errread, errwrite)
 except Exception:
 # Preserve original exception in case os.close raises.
 exc_type, exc_value, exc_trace = sys.exc_info()
 for fd in to_close:
 try:
 if mswindows:
 fd.Close()
 else:
 os.close(fd)
 except EnvironmentError:
 pass
On Windows, fd.Close() is always used.