Add test case for using auto_refresh_kwargs for authentication.

Also fix formatting.

requests_oauthlib/oauth2_session.py

@@ -419,12 +419,15 @@ def refresh_token(
         )
         kwargs.update(self.auto_refresh_kwargs)
 
-        auth = auth or kwargs.pop('auth', None)
-        client_id = kwargs.get('client_id')
-        client_secret = kwargs.get('client_secret', '')
+        auth = auth or kwargs.pop("auth", None)
+        client_id = kwargs.get("client_id")
+        client_secret = kwargs.get("client_secret", "")
 
         if client_id and (auth is None):
-            log.debug('Encoding client_id "%s" with client_secret as Basic auth credentials.', client_id)
+            log.debug(
+                'Encoding client_id "%s" with client_secret as Basic auth credentials.',
+                client_id,
+            )
             auth = requests.auth.HTTPBasicAuth(client_id, client_secret)
 
         body = self._client.prepare_refresh_body(
@@ -501,8 +504,10 @@ def request(
                     )
 
                     token = self.refresh_token(
-                        self.auto_refresh_url, client_id=client_id,
-                        client_secret=client_secret, **kwargs
+                        self.auto_refresh_url,
+                        client_id=client_id,
+                        client_secret=client_secret,
+                        **kwargs
                     )
                     if self.token_updater:
                         log.debug(

tests/test_oauth2_session.py

@@ -194,6 +194,21 @@ def fake_refresh_with_auth(r, **kwargs):
                 client_secret=self.client_secret,
             )
 
+        # auto refresh with auth from auto_refresh_kwargs
+        for client in self.clients:
+            sess = OAuth2Session(
+                client=client,
+                token=self.expired_token,
+                auto_refresh_url="https://i.b/refresh",
+                token_updater=token_updater,
+                auto_refresh_kwargs={
+                    "client_id": self.client_id,
+                    "client_secret": self.client_secret,
+                },
+            )
+            sess.send = fake_refresh_with_auth
+            sess.get("https://i.b")
+
     @mock.patch("time.time", new=lambda: fake_time)
     def test_token_from_fragment(self):
         mobile = MobileApplicationClient(self.client_id)