Add 404 Not Found error page.
Remove custom 401 Unauthorised error page config.

We don't want to display an error page for this. Perhaps 403 Forbidden,
though.
Add 500 Internal Server Error page.

Awwww, headache puppy.
Add 403 Forbidden error page.

I'm sorry Dave. I'm afraid I can't do that.
Enable custom error redirect for 403 Forbidden.
Merge branch 'feature/error-pages' into develop