bug: APNS may close a socket prematurely, resulting in an AttributeError

closes #862

autopush/router/apns2.py

@@ -124,6 +124,9 @@ def send(self, router_token, payload, apns_id,
             # re-established.
             stream_id = connection.request(
                 'POST', url=url, body=body, headers=headers)
+            # get_response() may return an AttributeError. Not really sure
+            # how it happens, but the connected socket may get set to None.
+            # We'll treat that as a premature socket closure.
             response = connection.get_response(stream_id)
             if response.status != 200:
                 reason = json.loads(response.read().decode('utf-8'))['reason']
@@ -135,7 +138,7 @@ def send(self, router_token, payload, apns_id,
                                   "your message {}".format(reason),
                     log_exception=False
                 )
-        except HTTP20Error:
+        except (HTTP20Error, AttributeError) as ex:
             connection.close()
             raise
         finally:

autopush/router/apnsrouter.py

@@ -142,7 +142,7 @@ def _route(self, notification, router_data):
         try:
             apns_client.send(router_token=router_token, payload=payload,
                              apns_id=apns_id)
-        except ConnectionError as ex:
+        except (ConnectionError, AttributeError) as ex:
             self.ap_settings.metrics.increment(
                 "updates.client.bridge.apns.connection_err",
                 self._base_tags