I'm having a problem while upgrading to the new version, I've searched for solutions but most of them didn't work, tried deleting PPAs and writing that command:
sudo dpkg --configure -a
But still the same error: This was likely caused by:
Unofficial software packages not provided by Ubuntu Please use the tool 'ppa-purge' from the ppa-purge package to remove software from a Launchpad PPA and try the upgrade again.
If none of this applies, then please report this bug using the command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal. If you want to investigate this yourself the log files in '/var/log/dist-upgrade' will contain details about the upgrade. Specifically, look at 'main.log' and 'apt.log'.
