Heads up. Recent changes to optparse and/or to its test are causing several spurious test failures, Here's a minimal incantation to get the first new failure of this kind: C:\Code\python\PCbuild>python -E -tt ../lib/test/regrtest.py test_optparse test_pep277 test_optparse test_pep277 test test_pep277 produced unexpected output: ********************************************************************** *** lines 2-4 of actual output doesn't appear in expected output after line 1: + u'\xdf-\u66e8\u66e9\u66eb' + ['???', '???', '??????', '????????????', '????G\xdf', 'Ge??-sa?', 'Gr\xfc\xdf-Gott', 'abc', 'ascii'] + [u'Gr\xfc\xdf-Gott', u'abc', u'ascii', u'\u0393\u03b5\u03b9\u03ac-\u03c3\u03b1\u03c2', u'\u0417\u0434\u0440\u0430\u043 2\u0441\u0442\u0432\u0443\u0439\u0442\u0435', u'\u05d4\u05e9\u05e7\u05e6\u05e5\u05e1', u'\u306b\u307d\u3093', u'\u66e8\u 05e9\u3093\u0434\u0393\xdf', u'\u66e8\u66e9\u66eb'] ********************************************************************** 1 test OK. 1 test failed: test_pep277 In all, with a complete test run, there are 15 spurious test failures on Windows now: 15 tests failed: test_pep277 test_pkg test_popen test_popen2 test_profile test_pyexpat test_regex test_rgbimg test_rotor test_scope test_thread test_threadedtempfile test_tokenize test_winreg test_xreadline No idea why. Offhand, from the symptoms it looks like a change may be sending stdout into a black hole. Constructs like sys.stdout = StringIO() ! self.assertRaises(self.parser.parse_args, (cmdline_args,), None, ! SystemExit, expected_output, ! self.redirected_stdout) sys.stdout = sys.__stdout__ in the patch certainly intensify that suspicion <wink>.