change from throwing a Http404 exception, which I believe will try to render a static 404.html template - and ironically triggers a 500 server error. Just create a HttpResponse and set the status_code to 404.

common/djangoapps/contentserver/middleware.py

@@ -21,7 +21,9 @@ class StaticContentServer(object):
                 try:
                     content = contentstore().find(loc)
                 except NotFoundError:
-                    raise Http404
+                    response = HttpResponse()
+                    response.status_code = 404
+                    return response
 
                 # since we fetched it from DB, let's cache it going forward
                 set_cached_content(content)