add oauth_token to auth function

Frust, Tobias (FWCC) - 111645 · Frust, Tobias (FWCC) - 111645 · commit a5f847cafbe2 · 2017-10-19T13:58:01.000+02:00
diff --git a/gitlab/__init__.py b/gitlab/__init__.py
@@ -179,7 +179,7 @@ def auth(self):
         The `user` attribute will hold a `gitlab.objects.CurrentUser` object on
         success.
         """
-        if self.private_token:
+        if self.private_token or self.oauth_token:
             self._token_auth()
         else:
             self._credentials_auth()
