Comment 6 for bug 1598489

Having seen anothe rof these bug nad marking it as Dup there is a new chance to get more info what might have happened.

I have tracked down two reasons issues like that happened for other cases, so in addition to the questions of comment #2 i'd want you to:
1. check for UCF related issues
   1.1 run 'debconf-show ucf' and report it here (resolve any issues listed if you can)
   1.2 apt install --reinstall ucf and then retry the upgrade above again
2. run "dpkg --verify" if anything isn't as it is supposed to be
3. some report dpkg DB being gone as related, has one of you touched/removed /var/lib/dpkg/info manually?