Update mock_settings.py as required for Django 2.2

Author: dannyroberts

Diff for: django_prbac/mock_settings.py

@@ -22,6 +22,7 @@
     'django.contrib.contenttypes',
     'django.contrib.sessions',
     'django.contrib.staticfiles',
+    'django.contrib.messages',
 
     # And this app
     'django_prbac',
@@ -30,3 +31,21 @@
 STATIC_URL = '/static/'
 
 ROOT_URLCONF = 'django_prbac.urls'
+
+MIDDLEWARE = [
+    'django.contrib.auth.middleware.AuthenticationMiddleware',
+    'django.contrib.messages.middleware.MessageMiddleware',
+    'django.contrib.sessions.middleware.SessionMiddleware',
+]
+
+TEMPLATES = [
+    {
+        'BACKEND': 'django.template.backends.django.DjangoTemplates',
+        'OPTIONS': {
+            'context_processors': [
+                'django.contrib.auth.context_processors.auth',
+                'django.contrib.messages.context_processors.messages',
+            ],
+        }
+    },
+]