Break KafkaClient poll if closed

Author: dpkp

kafka/client_async.py

@@ -551,6 +551,8 @@ def poll(self, timeout_ms=None, future=None):
         responses = []
         while True:
             with self._lock:
+                if self._closed:
+                    break
 
                 # Attempt to complete pending connections
                 for node_id in list(self._connecting):