Comment 5 for bug 860765

Thanks. Unfortunately this doesn't help us much. It showed that something in cups is wrong, it failed to start and create the /var/run/cups.sock socket, but it didn't fail with a nonzero exit code as it did in your original upgrade.

I tried to deliberately disable the socket in /etc/cups/cupsd.conf, and the upgrade still succeeds as expected.

Anyway, can you please attach /var/log/cups/error_log here? It might have the reason why it failed.