Comment 11 for bug 1780841

Not sure if this should get a new ticket, but if `snap debug connectivity` fails, the whole upgrade mysteriously aborts (user sees ```Reading state information... Done

Restoring original system state

Aborting
``` and `main.log` shows ```2018-12-12 21:24:20,067 DEBUG running Quirks.bionicPostInitialUpdate
2018-12-12 21:24:20,367 DEBUG abort called
``` with literally no other output anywhere.

`strace` is what finds the `snap debug connectivity` call, and `service snapd status` shows `Active: failed (Result: start-limit-hit)` - `service snapd start` fixes that and `do-release-upgrade` goes through fine.

(It's not just me, https://askubuntu.com/questions/1078692/cant-upgrade-ubuntu-16-04-to-18-04-lts/1100514 looks to be the same symptoms, but it wasn't until I'd figured out that `snap` was involved that I found this feature-ticket; I don't think it's widely known, I believe most users don't even know snap is *in* 16.04, and certainly won't notice `snapd` being broken without other hints...)