TIP! for the next time something like that happens :
- Start another SSH session to your Pi-Hole.
- Change the DNS Server used by the OS the way that applies to your situation.
- Restart the network service used by your OS.
You will now see the Pi-Hole update process finishing succesfully
Once everything is up and running again you can change the DNS Server used by your OS back to the Pi-Hole : 127.0.0.1