def test_invalidUmask(self):
        """
        If a value is given for the C{umask} option which cannot be parsed as
        an integer, L{UsageError} is raised by L{ServerOptions.parseOptions}.
        """
        config = twistd.ServerOptions()
        self.assertRaises(UsageError, config.parseOptions,
                          ['--umask', 'abcdef'])

        If a value is given for the C{umask} option which cannot be parsed as
        an integer, L{UsageError} is raised by L{ServerOptions.parseOptions}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_twistd.py