[1.9.x] Fixed #26280 -- Fixed cached template loader crash when loading nonexistent template.

        template_tuple = self.template_cache.get(key)

        # A cached previous failure:

        if template_tuple is TemplateDoesNotExist:

            raise TemplateDoesNotExist

            raise TemplateDoesNotExist(template_name)

        elif template_tuple is None:

            template, origin = self.find_template(template_name, template_dirs)

            if not hasattr(template, 'render'):

* Changed the admin's "permission denied" message in the login template to use

  ``get_username`` instead of ``username`` to support custom user models

  (:ticket:`26231`).

* Fixed a crash when passing a nonexistent template name to the cached template

  loader's ``load_template()`` method (:ticket:`26280`).

            "Cached loader failed to cache the TemplateDoesNotExist exception",

        )

    @ignore_warnings(category=RemovedInDjango20Warning)

    def test_load_nonexistent_cached_template(self):

        loader = self.engine.template_loaders[0]

        template_name = 'nonexistent.html'

        # fill the template cache

        with self.assertRaises(TemplateDoesNotExist):

            loader.find_template(template_name)

        with self.assertRaisesMessage(TemplateDoesNotExist, template_name):

            loader.get_template(template_name)

    def test_templatedir_caching(self):

        """

        #13573 -- Template directories should be part of the cache key.