update-manager failed to update: apt has no solutions

[bsy]

apt.log appears to be full of complaints about python2 packages. in any case, the update manager seems to have restored my system to a sane state. i haven't tried removing infrequently used python2 packages yet to see if that would help.

Description: Ubuntu 18.04.5 LTS
Release: 18.04

update-manager:
  Installed: 1:18.04.11.13
  Candidate: 1:18.04.11.13
  Version table:
 *** 1:18.04.11.13 500
        500 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
        500 http://archive.ubuntu.com/ubuntu bionic-updates/main i386 Packages
        100 /var/lib/dpkg/status
     1:18.04.11 500
        500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages
        500 http://archive.ubuntu.com/ubuntu bionic/main i386 Packages
update-manager-core:
  Installed: 1:18.04.11.13
  Candidate: 1:18.04.11.13
  Version table:
 *** 1:18.04.11.13 500
        500 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
        500 http://archive.ubuntu.com/ubuntu bionic-updates/main i386 Packages
        100 /var/lib/dpkg/status
     1:18.04.11 500
        500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages
        500 http://archive.ubuntu.com/ubuntu bionic/main i386 Packages

i expected a seamless upgrade to 20.04.

update-manager failed, but seems to have restored the system to a sane state.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.38
ProcVersionSignature: Ubuntu 4.15.0-118.119-generic 4.15.18
Uname: Linux 4.15.0-118-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.17
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Wed Sep 30 18:04:23 2020
DistributionChannelDescriptor:
 # This is a distribution channel descriptor
 # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
 canonical-oem-somerville-xenial-amd64-20160624-2
EcryptfsInUse: Yes
InstallationDate: Installed on 2017-02-19 (1319 days ago)
InstallationMedia: Ubuntu 16.04 "Xenial" - Build amd64 LIVE Binary 20160624-10:47
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-10-01 (0 days ago)
VarLogDistupgradeTermlog:

mtime.conffile..etc.update-manager.release-upgrades: 2020-09-30T17:59:57.212485

[bsy (bennet-yee)]

After removing python dbg packages, the upgrade succeeded.