Apt upgrade error: distro-info-data breaks distro-info

I'm running a server that has been recently upgraded in place from 16.04 to 18.04. The upgrade has generally been successful, although I am now getting an error relating to the 'distro-info-data' and 'distro-info' packages. When I run sudo apt upgrade, I get the following error as part of the output:

Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help resolve the situation:
 
The following packages have unmet dependencies:
 distro-info-data : Breaks: distro-info (< 0.18ubuntu0.18.04.1~) but 0.14ubuntu0.2 is to be installed
E: Broken packages

Full terminal output here: https://pastebin.com/eEA8N8HQ

Now I should say that during the upgrade, when it came time to ask me if I wanted to remove the obsolete packages, I didn't get a chance to state my intent either way, because when I went to look at the list - and I was keying directly into the server, not using SSH - the keyboard and my state in the upgrade process decided to have a divorce. I couldn't get back to any kind of menu and I just rebooted and hoped 18.04 would come up. It did, and as far as the things the server needs to do to earn its keep, it is still doing them, but I would like to find a way to get this little glitch resolved.

(Well, it might be a little glitch that belies a large underlying problem... Ulp!)

Update: Running sudo dist-upgrade says that 'ubuntu-advantage-tools' has been kept back / not upgraded. This pastebin includes that as well as a grep from /etc/apt/, which indicates a lot of 'xenial' where one ought to see 'bionic': https://pastebin.com/TmCsd7qY

Thanks very much!