middleware_classes is renamed middleware

bookshare/settings/settings.py

@@ -90,7 +90,7 @@ REST_FRAMEWORK = {
 
 MESSAGE_TAGS = {messages.ERROR: 'danger', }
 
-MIDDLEWARE_CLASSES = (
+MIDDLEWARE = (
     'django.middleware.common.CommonMiddleware',
     'django.contrib.sessions.middleware.SessionMiddleware',
     'django.contrib.auth.middleware.AuthenticationMiddleware',