do-release-upgrade 12.04 fails

[Paul Marxhausen]

Stable, well maintained, plain-vanilla 12.04 web server failed the "do-release-upgrade" procedure to 14.04 while calculating the differences. Message "An unresolvable problem occurred while calculating the upgrade.

This can be caused by:
* Upgrading to a pre-release version of Ubuntu
* Running the current pre-release version of Ubuntu
* Unofficial software packages not provided by Ubuntu

If none of this applies, then report this bug using the
command "ubuntu-bug ubuntu-release-upgrader-core""

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: update-manager (not installed)
ProcVersionSignature: Ubuntu 3.2.0-39.62-generic 3.2.39
Uname: Linux 3.2.0-39-generic x86_64
ApportVersion: 2.0.1-0ubuntu17.9
Architecture: amd64
Date: Tue Aug 11 08:19:07 2015
MarkForUpload: True
ProcEnviron:
 TERM=linux
 PATH=(custom, no user)
 LANG=POSIX
 SHELL=/bin/bash
SourcePackage: update-manager
Symptom: ubuntu-release-upgrader-core
UpgradeStatus: Upgraded to precise on 2015-08-11 (0 days ago)

[Paul Marxhausen (pmarxhausen)]

OK, I find a couple other people had this problem, and bug #1357566 seems to be pretty much the same. A contributor writes that he resolved this by removing libkrb5-3 and then the upgrade went smoothly.

I remember fighting with libkrb53 and libkrb5-3 when I updated to 12.04, because openssh-server was not working correctly. It's been too long and I don't remember but I THINK I had to remove libkrb53 and install libkrb5-3 to make openssh-server happy.

So it's not just Postgres that takes a hit from removing this. I'm not going to try removing libkrb5-3 and rerunning things just yet until I can do some more homework - maybe some testing on another server to see if I can remove it, run an upgrade, and then reinstall it.