Add method-level on_removing_rt trigger

Author: rayluo

oauth2cli/oauth2.py

@@ -396,16 +396,18 @@ def _obtain_token(self, grant_type, params=None, data=None, *args, **kwargs):
 
     def obtain_token_by_refresh_token(self, token_item, scope=None,
             rt_getter=lambda token_item: token_item["refresh_token"],
+            on_removing_rt=None,
             **kwargs):
         # type: (Union[str, dict], Union[str, list, set, tuple], Callable) -> dict
         """This is an "overload" which accepts a refresh token item as a dict,
         therefore this method can relay refresh_token item to event listeners.
 
-        :param refresh_token_item: A refresh token item came from storage
+        :param token_item: A refresh token item came from storage
         :param scope: If omitted, is treated as equal to the scope originally
             granted by the resource ownser,
             according to https://tools.ietf.org/html/rfc6749#section-6
         :param rt_getter: A callable used to extract the RT from token_item
+        :param on_removing_rt: If absent, fall back to the one defined in initialization
         """
         if isinstance(token_item, str):
             # Satisfy the L of SOLID, although we expect caller uses a dict
@@ -415,7 +417,7 @@ def obtain_token_by_refresh_token(self, token_item, scope=None,
             resp = super(Client, self).obtain_token_by_refresh_token(
                     rt_getter(token_item), scope=scope, **kwargs)
             if resp.get('error') == 'invalid_grant':
-                self.on_removing_rt(token_item)  # Discard old RT
+                (on_removing_rt or self.on_removing_rt)(token_item)  # Discard old RT
             if 'refresh_token' in resp:
                 self.on_updating_rt(token_item, resp['refresh_token'])
             return resp