Propagate exception when moves are cancelled

This ensures an action using the stage is cancelled properly, rather
than the stage swallowing the cancellation.

Author: rwb27

src/labthings_sangaboard/proscan.py

@@ -93,9 +93,9 @@ def move_relative(self, cancel: CancelHook, block_cancellation: bool=False, x: O
                 try:
                     while self.is_moving:
                         cancel.sleep(0.05)
-                except InvocationCancelledError:
-                    logging.info("Aborting move due to invocation cancellation, using `I`,")
+                except InvocationCancelledError as e:
                     self.query("I")
+                    raise e
             self.moving=False
 
     @thing_property