Bug 35553 introduced a workaround to a python bug in subprocess.open(). Unfortunately, the workaround causes new-run-webkit-tests to fail outright on windows because the parameter (close_fds) isn't supported.
Created attachment 49844 [details] Patch
Comment on attachment 49844 [details] Patch ok.
Fix landed as http://trac.webkit.org/changeset/55434 .