fixed #897: compatibility with aio-pika>=7 (#900)

src/socketio/asyncio_aiopika_manager.py

@@ -93,7 +93,7 @@ class AsyncAioPikaManager(AsyncPubSubManager):  # pragma: no cover
 
                 async with self.listener_queue.iterator() as queue_iter:
                     async for message in queue_iter:
-                        with message.process():
+                        async with message.process():
                             yield pickle.loads(message.body)
             except Exception:
                 self._get_logger().error('Cannot receive from rabbitmq... '