fix it?

txupnp/gateway.py

@@ -81,6 +81,7 @@ class Gateway(object):
         log.info("querying %s", self.location)
         response = yield treq.get(self.location)
         response_xml = yield response.content()
+        if response_xml:
             self._device = RootDevice(response_xml)
             if not self._device.devices or not self._device.services:
                 log.error("failed to parse device: \n%s", response_xml)