An unresolvable problem occurred while calculating the upgrade

[Gus]

An unresolvable problem occurred while calculating the upgrade

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.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubuntu-release-upgrader-core 1:16.04.29
ProcVersionSignature: Ubuntu 4.4.0-169.198-generic 4.4.197
Uname: Linux 4.4.0-169-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.21
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Sat Nov 30 15:59:57 2019
InstallationDate: Installed on 2017-02-14 (1019 days ago)
InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to xenial on 2019-11-30 (0 days ago)
VarLogDistupgradeTermlog:

mtime.conffile..etc.update-manager.release-upgrades: 2019-11-30T15:56:07.959923

[Gus (gus99)]

I don't want to comment, I want to upgrade :-(

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.