Conditionalize close_fds argument of subprocess.Popen when on Windows

The close_fds argument to subprocess.Popen is not supported on Windows when redirecting the standard streams. You receive the following ValueError when using a patch process rather than the patch library.

    ValueError: close_fds is not supported on Windows platforms if you redirect stdin/stdout/stderr

Checking against sys.platform and only setting this argument to True on non-Windows seems like the easiest fix, and it works.