94457732c1 changed this from:
```py
event_name = payload.get("event_name", payload.get("object_kind")).tame(check_string)
```
...to:
```py
event_name = payload.get("event_name", payload["object_kind"]).tame(check_string)
```
Which causes a failure when `event_name` exists but `object_kind` does
not, since the default is evaluated first.
Switch to an `if` statement to clarify the fallbacks better.
Alex Vandiver