Comment 2 for bug 1781440

I upgraded from Bionic to Cosmic by editing /etc/apt/sources.list replacing all occurences of bionic by cosmic and then running

sudo apt update
sudo apt dist-upgrade

After some time the error occured and I cleaned up with

sudo apt install -f

and completed the upgrade with another

sudo apt dist-upgrade

which this time completed without errors.

In the end I did

sudo apt autoremove

to finish up.

So the error occured only once and after cleaning up I could complete the upgrade.