Comment 46 for bug 1670959

And looks like we need to find out what is adding 127.0.0.1 to resolv.conf. It could come from many different sources, like a nameserver configuration in some /etc/network/interfaces carried over from xenial, or something in network-manager, etc. I guess you could start with a brute-force grep -r on /etc for 127.0.0.1?