Minor addition to chatroom test

tests/chatroom_server.py

@@ -20,6 +20,10 @@ async def message_handler(q: aiosched.Queue):
             logging.info(f"Got message {msg!r} with the following payload: {payload}")
     except Exception as e:
         logging.error(f"An exception occurred in the message handler -> {type(e).__name__}: {e}")
+    except aiosched.errors.Cancelled:
+        logging.warning(f"Cancellation detected, message handler shutting down")
+        # Propagate the cancellation
+        raise
 
 
 async def serve(bind_address: tuple):