def test_umask(self):
        """
        The value given for the C{umask} option is parsed as an octal integer
        literal.
        """
        config = twistd.ServerOptions()
        config.parseOptions(['--umask', '123'])
        self.assertEqual(config['umask'], 83)
        config.parseOptions(['--umask', '0123'])
        self.assertEqual(config['umask'], 83)

        The value given for the C{umask} option is parsed as an octal integer
        literal.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_twistd.py