sudo do-release-upgrade and it fails with the following error:
Calculating the changes Could not calculate the upgrade An unresolvable problem occurred while calculating the upgrade. This can be caused by: * Upgrading to a pre-release version of Ubuntu * Running the current pre-release version of Ubuntu * Unofficial software packages not provided by Ubuntu If none of this applies, then please report this bug using the command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal. Restoring original system state
/var/log/dist-upgrade/main.log https://www.dropbox.com/s/3gf1tg8uxmn75jq/main.log?dl=0 /var/log/dist-upgrade/apt.log https://www.dropbox.com/s/79i2mf320pvg3bl/apt.log?dl=0
I don't understand why package manager can not resolve this and what package is the source of this problem.
Appreciate any help.