504 error when searching on k8s.sgdev.org with indexed search disabled

Created by: ryan-blunden

1. Go to https://k8s.sgdev.org/site-admin/configuration
2. set search.index.enabled to false
3. Search for (hunk|repository)resolver timeout:1000s
4. The request should time out with, page displays Unexpected HTTP error: 504.

The error displayed to the user should be more user-friendly and explain what happened instead of just the unexpected error message.