[py3] Fixed middleware_exceptions tests.

from __future__ import unicode_literals

import sys

import types

from django import http

from django.core import signals

                # Complain if the view returned None (a common error).

                if response is None:

                    try:

                        view_name = callback.func_name # If it's a function

                    except AttributeError:

                        view_name = callback.__class__.__name__ + '.__call__' # If it's a class

                    if isinstance(callback, types.FunctionType):    # FBV

                        view_name = callback.__name__

                    else:                                           # CBV

                        view_name = callback.__class__.__name__ + '.__call__'

                    raise ValueError("The view %s.%s didn't return an HttpResponse object." % (callback.__module__, view_name))

                # If the response supports deferred rendering, apply template