Fixed error code in auth handler (finally closes #282)

server.py

@@ -586,7 +586,7 @@ def auth(): # For use with nginx auth_request
 				ORDER BY perm.video_id DESC, perm.lecture_id DESC, perm.course_id DESC''',
 				url)
 	if not perms:
-		return "Not allowed", 403
+		return "Not found", 404
 	auth = request.authorization
 	username = password = None
 	if auth: