[Bug 2030521] [NEW] Ubuntu upgrade from LTS 18.04 to LTS 20.04 fails due to Launchpad PPA error when none on machine

[Christian Rockwell]

Public bug reported:

1) Release: Ubuntu 18.04.6 LTS.
2) Package version: N: Unable to locate package pkgname (result of executing "apt-cache policy pkgname").
3) I expected the updater to upgrade my os to LTS 20.04 (either via GUI or running "sudo do-release-upgrade
".
4) I keep getting an error saying:
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.

I've deleted the "git-core" PPA via the "Software & Updates app > Other
Software" as well as deleting the PPA files via the Nautilus UI. The
latter approach seemed to have completely removed them, but the error
still persists.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.45
ProcVersionSignature: Ubuntu 5.4.0-150.167~18.04.1-generic 5.4.233
Uname: Linux 5.4.0-150-generic x86_64
NonfreeKernelModules: lkp_Ubuntu_5_4_0_150_167_generic_96 nvidia_modeset nvidia
ApportVersion: 2.20.9-0ubuntu7.29
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Mon Aug  7 10:55:33 2023
InstallationDate: Installed on 2020-05-29 (1165 days ago)
InstallationMedia: Ubuntu 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805)
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 2023-08-07 (0 days ago)
VarLogDistupgradeTermlog:

** Affects: ubuntu-release-upgrader (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug bionic dist-upgrade third-party-packages

** Attachment added: "Main log from latest upgrade attempt"
   https://bugs.launchpad.net/bugs/2030521/+attachment/5690911/+files/main.log

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https://bugs.launchpad.net/bugs/2030521

Title:
  Ubuntu upgrade from LTS 18.04 to LTS 20.04 fails due to Launchpad PPA
  error when none on machine

Status in ubuntu-release-upgrader package in Ubuntu:
  New

Bug description:
  1) Release: Ubuntu 18.04.6 LTS.
  2) Package version: N: Unable to locate package pkgname (result of executing "apt-cache policy pkgname").
  3) I expected the updater to upgrade my os to LTS 20.04 (either via GUI or running "sudo do-release-upgrade
  ".
  4) I keep getting an error saying:
  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.

  I've deleted the "git-core" PPA via the "Software & Updates app >
  Other Software" as well as deleting the PPA files via the Nautilus UI.
  The latter approach seemed to have completely removed them, but the
  error still persists.

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: ubuntu-release-upgrader-core 1:18.04.45
  ProcVersionSignature: Ubuntu 5.4.0-150.167~18.04.1-generic 5.4.233
  Uname: Linux 5.4.0-150-generic x86_64
  NonfreeKernelModules: lkp_Ubuntu_5_4_0_150_167_generic_96 nvidia_modeset nvidia
  ApportVersion: 2.20.9-0ubuntu7.29
  Architecture: amd64
  CrashDB: ubuntu
  CurrentDesktop: ubuntu:GNOME
  Date: Mon Aug  7 10:55:33 2023
  InstallationDate: Installed on 2020-05-29 (1165 days ago)
  InstallationMedia: Ubuntu 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805)
  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 2023-08-07 (0 days ago)
  VarLogDistupgradeTermlog:

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