'Returns ``None`` if the metadata URL is not found.'

def test_not_found(self):

    listening = webserver_for_test(self, url_path='/some/other/path', response_content=json.dumps({}))
    connecting = listening.addCallback((lambda port: deferToThread(metadata_from_service, metadata_service_endpoint=next(((a.host, a.port) for a in [port.getHost()])))))
    def check(result):
        self.assertIs(None, result)
    checking = connecting.addCallback(check)
    return checking
