code: def test_error_router_falls_back_to_original(self, app, mocker):
      class ProgrammingBlunder(Exception):
          pass
  
      blunder = ProgrammingBlunder(
          "This exception needs to be detectable"
      )
  
      def raise_blunder(arg):
          raise blunder
  
      api = restplus.Api(app)
      app.handle_exception = mocker.Mock()
      api.handle_error = mocker.Mock(side_effect=raise_blunder)
      api._has_fr_route = mocker.Mock(return_value=True)
      exception = mocker.Mock(spec=HTTPException)
  
      api.error_router(app.handle_exception, exception)
  
      app.handle_exception.assert_called_with(blunder)
  
imports: from __future__ import unicode_literals
  import json
  import logging
  import pytest
  from flask import Blueprint, abort
  from flask.signals import got_request_exception
  from werkzeug.exceptions import HTTPException, BadRequest, NotFound, Aborter
  from werkzeug.http import quote_etag, unquote_etag
  import flask_restplus
label_desc: Use image node_id 31 for calling the ErrorsTest obj's underlying member method code with example usage: obj.test_error_router_falls_back_to_original(app, mocker) without return types