My Pi-hole box is (was) using itself for name resolution.
I've just had an upgrade break as something in the process stopped the DNS server but the next step then tried to do something network related which failed as it couldn't get an IP address.
A quick discussion on twitter found you don't recommend pointing the host at itself as a resolver, this makes sense now I've had it mess things up, but was a pain at the time.
I'm suggesting you check /etc/resolv.conf to see if it is pointing at localhost and, if it is, then flag an alert in the installer to warn people to use something different. I agree not everyone will read it, but it may help some people.