def test_noProxyPassthrough(self):
        """
        The CGI script is never called with the Proxy header passed through.
        """
        cgiFilename = self.writeCGI(HEADER_OUTPUT_CGI)

        portnum = self.startServer(cgiFilename)
        url = "http://localhost:%d/cgi" % (portnum,)
        url = url.encode("ascii")

        agent = client.Agent(reactor)

        headers = http_headers.Headers({b"Proxy": [b"foo"],
                                        b"X-Innocent-Header": [b"bar"]})
        d = agent.request(b"GET", url, headers=headers)

        def checkResponse(response):
            headers = json.loads(response.decode("ascii"))
            self.assertEqual(
                set(headers.keys()),
                {"HTTP_HOST", "HTTP_CONNECTION", "HTTP_X_INNOCENT_HEADER"})

        d.addCallback(client.readBody)
        d.addCallback(checkResponse)
        return d

        The CGI script is never called with the Proxy header passed through.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_cgi.py