Ref T11589. When we hit a fatal setup issue (essentially always a connection failure) after we've already survived them on at least one request, we can be pretty sure a server went down and that the problem is not a setup/configuration issue.

In this case, show a friendlier error page instead of the fairly detailed technical one.

• Broke MySQL config.
• Restarted Apache.
• Got the "admin/setup" error page:

• Fixed the MySQL config.
• Loaded any page, to put us "in flight".
• Broke MySQL config.
• Loaded any page.
• Got the friendly "in flight" error page:

If you want to design this better, easiest way to get to it is:

• Set mysql.port to 9999 in conf/local/local.json.
• Reload any page while already running (don't restart).