I tried to upgrade an Debian box that was left a bit behind today and apt-get upgrade failed somewhere between libssl1.0.0 and python2.7-minimal (among a few other packages) being depended on each other and the installation script gave up. apt-get upgrade -f refused also.
If you google around this is a problem that many people had with many different causes and solutions that may or may not work in your case. So here is another one that I copy-pasted from the internets that worked in this particular case. In file /var/cache/debconf/config.dat I added:
Name: libraries/restart-without-asking Template: libraries/restart-without-asking Value: true Owners: libssl1.0.0 Flags: seen