docs: def _on_auth(self, user):
          """
          This is called when login with OpenID succeeded and it's not
          necessary to figure out if this is the users's first login or not.
          """
          app = current_app._get_current_object()
          if not user:
              # Google auth failed.
              login_error.send(app, user=None)
              abort(403)
          session["openid"] = user
          login.send(app, user=user)
          return redirect(request.args.get("next", None) or request.referrer or "/")