Fixed #22362 -- Improved AuthenticationMiddleware assertion message.

Thanks Keryn Knight.

django/contrib/auth/middleware.py

@@ -13,8 +13,12 @@ def get_user(request):
 
 class AuthenticationMiddleware(object):
     def process_request(self, request):
-        assert hasattr(request, 'session'), "The Django authentication middleware requires session middleware to be installed. Edit your MIDDLEWARE_CLASSES setting to insert 'django.contrib.sessions.middleware.SessionMiddleware'."
-
+        assert hasattr(request, 'session'), (
+            "The Django authentication middleware requires session middleware "
+            "to be installed. Edit your MIDDLEWARE_CLASSES setting to insert "
+            "'django.contrib.sessions.middleware.SessionMiddleware' before "
+            "'django.contrib.auth.middleware.AuthenticationMiddleware'."
+        )
         request.user = SimpleLazyObject(lambda: get_user(request))