A while back @mythmon and I had a conversation about this. I interpreted the Django docs as saying this is the required signature for signal handlers, but I've seen a few places that use different signatures and I think my interpretation of the docs is wrong and that @mythmon was right in his gut feeling that this isn't very pythonic in the first place, so it's weird Django would do that. Django does make sure you have a `**kwargs` catch-all.

Anyhow, given you pull out the rev, you should probably do:

```
def on_revision_save(sender, instance, **kwargs):
```

For example: https://github.com/mozilla/kuma/blob/master/apps/wiki/tasks.py#L128