update to 20.04 fails

[Ge Timmer]

2020-10-15 12:13:12,549 ERROR Dist-upgrade failed: 'E:Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.'
2020-10-15 12:13:12,550 DEBUG abort called
2020-10-15 12:13:12,586 DEBUG openCache()
2020-10-15 12:13:14,742 DEBUG Comparing 4.15.0-118 with
2020-10-15 12:13:14,743 DEBUG Comparing 4.15.0-121 with 4.15.0-118
2020-10-15 12:13:14,950 DEBUG /openCache(), new cache size 100372

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.38
ProcVersionSignature: Ubuntu 4.15.0-121.123-generic 4.15.18
Uname: Linux 4.15.0-121-generic x86_64
NonfreeKernelModules: talpa_vfshook talpa_pedconnector talpa_pedevice talpa_vcdevice talpa_core talpa_linux talpa_syscallhook nvidia_modeset nvidia
ApportVersion: 2.20.9-0ubuntu7.18
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Thu Oct 15 12:13:50 2020
InstallationDate: Installed on 2016-04-08 (1651 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-10-15 (0 days ago)