Upgrade to focal 20.04 doesn't work

[Andreas Landhäußer]

Upgrade doesn't work
main.log containing:
2020-09-29 18:08:39,187 DEBUG Installing 'python-is-python2' (python-minimal was installed on the system)
2020-09-29 18:08:48,888 ERROR Dist-upgrade failed: 'E:Unable to correct problems, you have held broken packages.'
2020-09-29 18:08:48,890 DEBUG abort called
2020-09-29 18:08:48,892 DEBUG openCache()
2020-09-29 18:08:52,086 DEBUG Comparing 4.15.0-118 with
2020-09-29 18:08:52,087 DEBUG Comparing 4.15.0-119 with 4.15.0-118
2020-09-29 18:08:52,378 DEBUG /openCache(), new cache size 100196

Dunno whats happening here

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.39
ProcVersionSignature: Ubuntu 4.15.0-119.120-generic 4.15.18
Uname: Linux 4.15.0-119-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.18
Architecture: amd64
CrashDB: ubuntu
Date: Tue Sep 29 18:23:46 2020
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-09-29 (0 days ago)
VarLogDistupgradeTermlog: