TMSS-421: added new MessageHandlerError. reject message if caught.

LCS/Messaging/python/messaging/exceptions.py

@@ -65,3 +65,15 @@ class MessagingTimeoutError(MessagingError, TimeoutError):
     """
     pass
 
+
+class MessageHandlerError(MessagingError):
+    """
+    raised upon handling a message
+    """
+    pass
+
+class MessageHandlerUnknownSubjectError(MessageHandlerError):
+    """
+    raised upon handling a message with an unknown subject
+    """
+    pass

LCS/Messaging/python/messaging/messagebus.py

@@ -1570,6 +1570,9 @@ class BusListener:
                             if isinstance(e, TimeoutError):
                                 logger.error("Handling of %s timed out: %s", lofar_msg, e)
                                 receiver.reject(lofar_msg, requeue=True)
+                            elif isinstance(e, MessageHandlerError):
+                                logger.error("Could not handle message %s: %s", lofar_msg, e)
+                                receiver.reject(lofar_msg, requeue=False)
                             else:
                                 logger.exception("Handling of %s failed. Rejecting message. Error: %s", lofar_msg, e)
                                 receiver.reject(lofar_msg, requeue=False)