Implement abstract method can.Listener.stop() in MessageListener. (#422)

Author: acolomb

canopen/network.py

@@ -363,6 +363,9 @@ def on_message_received(self, msg):
             # Exceptions in any callbaks should not affect CAN processing
             logger.error(str(e))
 
+    def stop(self) -> None:
+        """Override abstract base method to release any resources."""
+
 
 class NodeScanner:
     """Observes which nodes are present on the bus.