[Bug 1787862] [NEW] error "could not calculate the upgrade" while upgrading Kubuntu 17.10 to 18.04

[tuxi]

Public bug reported:

I uninstalled already ppa-backports with "ppa-purge" but still get the
same error.

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: ubuntu-release-upgrader-core 1:17.10.11
ProcVersionSignature: Ubuntu 4.13.0-46.51-generic 4.13.16
Uname: Linux 4.13.0-46-generic x86_64
ApportVersion: 2.20.7-0ubuntu3.9
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: KDE
Date: Mon Aug 20 00:25:07 2018
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to artful on 2018-08-19 (0 days ago)
VarLogDistupgradeTermlog:

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


** Tags: amd64 apport-bug artful dist-upgrade

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https://bugs.launchpad.net/bugs/1787862

Title:
  error "could not calculate the upgrade" while upgrading Kubuntu 17.10
  to 18.04

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

Bug description:
  I uninstalled already ppa-backports with "ppa-purge" but still get the
  same error.

  ProblemType: Bug
  DistroRelease: Ubuntu 17.10
  Package: ubuntu-release-upgrader-core 1:17.10.11
  ProcVersionSignature: Ubuntu 4.13.0-46.51-generic 4.13.16
  Uname: Linux 4.13.0-46-generic x86_64
  ApportVersion: 2.20.7-0ubuntu3.9
  Architecture: amd64
  CrashDB: ubuntu
  CurrentDesktop: KDE
  Date: Mon Aug 20 00:25:07 2018
  PackageArchitecture: all
  SourcePackage: ubuntu-release-upgrader
  UpgradeStatus: Upgraded to artful on 2018-08-19 (0 days ago)
  VarLogDistupgradeTermlog:

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