old_contents: # -*- coding: utf-8 -*-
  from __future__ import print_function
  from __future__ import unicode_literals
  from __future__ import division
  
  
  class InvalidInstanceException(Exception):
      pass
  
  
  class FeatureNotEnabledException(Exception):
      pass
  
new_contents: # -*- coding: utf-8 -*-
  from __future__ import print_function
  from __future__ import unicode_literals
  from __future__ import division
  
  import json
  from django.http import HttpResponseForbidden
  
  
  class InvalidInstanceException(Exception):
      pass
  
  
  class FeatureNotEnabledException(Exception):
      pass
  
  
  class JSONResponseForbidden(HttpResponseForbidden):
      def __init__(self, *args, **kwargs):
          super(JSONResponseForbidden, self).__init__(
              json.dumps({'error': 'Permission Denied'}),
              *args,
              content_type='application/json',
              **kwargs)
  
subject: Add JSONResponseForbidden class