          accept_list = ['application/pickle', 'application/json']
          PRenderer = self.get_renderer_mock('application/pickle')
          JRenderer = self.get_renderer_mock('application/json')
  
          renderers = (PRenderer, JRenderer)
          response = self.get_response(accept_list=accept_list, renderers=renderers)
          renderer, media_type = response._determine_renderer()
          self.assertEqual(media_type, 'application/pickle')
          self.assertTrue(isinstance(renderer, PRenderer))
  
          renderers = (JRenderer,)
 
</s> remove         PRenderer = self.get_renderer_mock('application/pickle')
        JRenderer = self.get_renderer_mock('application/json')
 </s> add         prenderer = self.get_renderer_mock('application/pickle')
        jrenderer = self.get_renderer_mock('application/json') </s> remove         self.assertTrue(isinstance(renderer, PRenderer))
 </s> add         self.assertTrue(renderer, prenderer) </s> remove         renderers = (JRenderer,)
        response = self.get_response(accept_list=accept_list, renderers=renderers)
 </s> add         response = self.get_response(accept_list=accept_list, renderers=(jrenderer,)) </s> remove         self.assertTrue(isinstance(renderer, JRenderer))
 </s> add         self.assertTrue(renderer, jrenderer)

    def test_determine_renderer_default(self):
        """
        Test determine renderer when Accept was not specified.
        """
        prenderer = self.get_renderer_mock('application/pickle')

        response = self.get_response(accept_list=None, renderers=(prenderer,))
        renderer, media_type = response._determine_renderer()
        self.assertEqual(media_type, '*/*')
        self.assertTrue(renderer, prenderer) </s> remove         renderers = (PRenderer,)
        response = self.get_response(accept_list=accept_list, renderers=renderers)
        self.assertRaises(ErrorResponse, response._determine_renderer)
 </s> add         response = self.get_response(accept_list=accept_list, renderers=(prenderer,))
        self.assertRaises(ImmediateResponse, response._determine_renderer)
        response = self.get_response(accept_list=accept_list, renderers=(prenderer, jrenderer))
          accept_list = ['application/pickle', 'application/json']
          PRenderer = self.get_renderer_mock('application/pickle')
          JRenderer = self.get_renderer_mock('application/json')
  
        response = self.get_response(accept_list=accept_list, renderers=(prenderer, jrenderer))
        response = self.get_response(accept_list=accept_list, renderers=(prenderer, jrenderer))
          renderer, media_type = response._determine_renderer()
          self.assertEqual(media_type, 'application/pickle')
          self.assertTrue(isinstance(renderer, PRenderer))
  
          renderers = (JRenderer,)
keep keep keep keep replace replace keep keep keep keep keep
 cleaned a bit Response/ResponseMixin code, added some documentation + renamed ErrorResponse to ImmediateResponse 
djangorestframework/tests/response.py