Put static server middleware after the middleware it requires

lms/envs/common.py

@@ -542,7 +542,6 @@ TEMPLATE_LOADERS = (
 )
 
 MIDDLEWARE_CLASSES = (
-    'contentserver.middleware.StaticContentServer',
     'request_cache.middleware.RequestCache',
     'django_comment_client.middleware.AjaxExceptionMiddleware',
     'django.middleware.common.CommonMiddleware',
@@ -551,6 +550,7 @@ MIDDLEWARE_CLASSES = (
     # Instead of AuthenticationMiddleware, we use a cached backed version
     #'django.contrib.auth.middleware.AuthenticationMiddleware',
     'cache_toolbox.middleware.CacheBackedAuthenticationMiddleware',
+    'contentserver.middleware.StaticContentServer',
 
     'django.contrib.messages.middleware.MessageMiddleware',
     'track.middleware.TrackMiddleware',