Comment 4 for bug 538839

I have been victim of the same problem (only in my case it was kvm-pxe that couldn't be upgraded).

During dist-upgrade, got the message:
Could not install '/var/cache/apt/archives/kvm-pxe_5.4.4-1ubuntu1.1_all.deb'
The upgrade will continue but the '/var/cache/apt/archives/kvm-pxe_5.4.4-1ubuntu1.1_all.deb' package may not be in a working state. Please consider submitting a bug report about it. unable to install new version of `/usr/share/kvm/pxe-e1000.bin': No such file or directory
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while setting up package kvm-pxe, got the message:
package kvm-pxe is already installed and configured
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The final message from dist-upgrade was:
Could not install the upgrades

The upgrade is now aborted. Your system could be in an unusable state. A recovery will run now (dpkg --configure -a).
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Didn't prompt for restart at the end.

As such, I was left with an incomplete upgrade. Although it is running, I don't trust the system now...

There are no clues as to how to finish the upgrade. For the end user, it is unclear whether the system is ok or not. Visually it is inconsistent. And I guess there might be some real issues, besides the cosmetic ones.
So, I would mark this bug's importance as medium or high.

I sugest two things:
1- the dist-upgrade shouldn't abort if at least all meta-packages were installed (the desktop). One package that didn't upgrade shouldn't be enough to abort the upgrade past the 'no-rollback' point.In a server environment it might be done differently.
2- if dist-upgrade aborts after no-rollback point, then it should provide the means to resume whatever it should have done, after the user (eventually) fixes the issues.

I'll try to find how to implement that, but I don't have much experience with python...