Comment 2 for bug 717397

Hello Greg (and duplicate reporters), thanks for taking the time to file this bug report!

So unfortunately, this is likely the result of the squid process having disappeared because of bug #573853 , which ironically was fixed in the package that you are all trying to install.

This is a temporary problem, and the way to alleviate it is to kill squid off manually (it may still be running despite upstart having lost track of it), and then start it manually.

These three commands may print errors (and may leave your system in a bad state, so please be cautious), but should lead to the upgrade finishing:

sudo stop squid
sudo killall squid
sudo start squid
sudo dpkg --configure -a

Unfortunately, given the nature of the bug fixed there's no safe way that I have come up with to plan for this possible failure and get around it in the postinst. Given that, I believe this bug has to be closed as Won't Fix.

If someone comes up with a better way to handle the upgrade when the squid job is in an unknown state, then please re-open it.