Add the Squid error page to Varnish

Change-Id: I23addd9b1db5fa98394855757ec130458d9245a6
Make the error page nicer.

Change-Id: Ide9bfd888ec215dc94c05ec5b61bcab0643222e7
Merge "Add the Squid error page to Varnish" into production
Merge "Make the error page nicer." into production