delete unused imports from opds_catalog/middleware.py

from django.http import HttpResponse

from django.contrib import auth

from django.core.exceptions import ImproperlyConfigured

from django.core.urlresolvers import resolve

from django.utils import translation

from django.utils.cache import add_never_cache_headers

from django.middleware.cache import FetchFromCacheMiddleware as DjangoFetchFromCacheMiddleware

#from opds_catalog import settings

from constance import config

class FetchFromCacheMiddleware(DjangoFetchFromCacheMiddleware):

#    def process_response(self, request, response):

#        if not request.user.is_authenticated():

#            add_never_cache_headers(response)

#        return response

    def process_request(self, request):

        if not request.user.is_authenticated():

            return None