Merge branch 'customizable-on_obtaining_tokens' into dev

Author: rayluo

oauth2cli/oauth2.py

@@ -770,7 +770,6 @@ def obtain_token_by_refresh_token(self, token_item, scope=None,
             rt_getter=lambda token_item: token_item["refresh_token"],
             on_removing_rt=None,
             on_updating_rt=None,
-            on_obtaining_tokens=None,
             **kwargs):
         # type: (Union[str, dict], Union[str, list, set, tuple], Callable) -> dict
         """This is an overload which will trigger token storage callbacks.