Switch from concurrent.futures.CancelledError to asyncio.CancelledError

Since Python 3.8, the latter does not inherit from the former anymore.

qwarc/__init__.py

@@ -250,7 +250,7 @@ class QWARC:
 				item = future.item
 			try:
 				future.result()
-			except concurrent.futures.CancelledError as e:
+			except asyncio.CancelledError as e:
 				# Got cancelled, nothing we can do about it, but let's log a warning if it's a process task
 				if future.taskType == 'process':
 					logging.error(f'Task for {future.itemType}:{future.itemValue} cancelled: {future!r}')