def test_missingPROXYHeaderValue(self):
        """
        Test that an exception is raised when the PROXY header is missing.
        """
        self.assertRaises(
            InvalidProxyHeader,
            _v1parser.V1Parser.parse,
            b'NOTPROXY ',
        )

        Test that an exception is raised when the PROXY header is missing.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/protocols/haproxy/test/test_v1parser.py