upgrade from 16.04 to 18.04 uncalculatable due to fpc packages

[Luiz Coutinho]

[Impact]
Upgrades from 16.04 to 18.04 might fail if fpc packages are installed, as fp-units-base-3.0.4 Breaks fp-units-misc-3.0.0 (<= 3.0.0+dfsg-2); a leftover from fp-units-base-3.0.0 that should have been removed (all paths in the deb are versioned).

[Test case]
1. Extract dpkg status from apt clone system state in comment #1 and run apt dist-upgrade against it in a bionic system
2. Restore apt-clone and run ubuntu-release-upgrader

[Regression potential]
Since all paths are versioned, there should be no regressions.

[Original bug report]

it aborts in second step.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubuntu-release-upgrader-core 1:16.04.25
ProcVersionSignature: Ubuntu 4.4.0-131.157-generic 4.4.134
Uname: Linux 4.4.0-131-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Fri Aug 10 11:06:26 2018
InstallationDate: Installed on 2015-06-30 (1137 days ago)
InstallationMedia: Ubuntu 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.2)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to xenial on 2018-08-10 (0 days ago)
VarLogDistupgradeTermlog:

modified.conffile..etc.update-manager.release-upgrades: [modified]
mtime.conffile..etc.update-manager.release-upgrades: 2018-08-10T07:52:29.705103

[Brian Murray (brian-murray)]

I was able to recreate this bug by using the apt-clone file in it, after restoring the clone file the upgrade failed to calculate. When I removed the fpc package the upgrade was calculatable so it seems to be an issue with the fpc packages.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Julian Andres Klode (juliank)]

I believe it's a problem with fp-units-base-3.0.4 Breaks fp-units-misc-3.0.0 (<= 3.0.0+dfsg-2), as that prevents the old versions from remaining installed. Needs verification to make sure.

[Julian Andres Klode (juliank)]

Just verified, this solves the bug.

[Launchpad Janitor (janitor)]

This bug was fixed in the package fpc - 3.0.4+dfsg-20ubuntu1

---------------
fpc (3.0.4+dfsg-20ubuntu1) cosmic; urgency=medium

  * Remove wrong fp-units-base-3.0.4 Breaks fp-units-misc-3.0.0, this breaks
    upgrades from xenial (LP: #1786486)

 -- Julian Andres Klode <email address hidden> Wed, 29 Aug 2018 22:34:16 +0200

[Brian Murray (brian-murray)]

Hello Luiz, or anyone else affected,

Accepted fpc into bionic-proposed. The package will build now and be available at https://launchpad.net/ubuntu/+source/fpc/3.0.4+dfsg-18ubuntu2 in a few hours, and then in the -proposed repository.

Please help us by testing this new package. See https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how to enable and use -proposed.Your feedback will aid us getting this update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug, mentioning the version of the package you tested and change the tag from verification-needed-bionic to verification-done-bionic. If it does not fix the bug for you, please add a comment stating that, and change the tag to verification-failed-bionic. In either case, without details of your testing we will not be able to proceed.

Further information regarding the verification process can be found at https://wiki.ubuntu.com/QATeam/PerformingSRUVerification . Thank you in advance!

[Julian Andres Klode (juliank)]

I generated a bionic container, and then ran apt upgrade against the dpkg status file in it, that is:

lxc exec splendid-flea -- apt -o Dir::State::Status=$PWD/var/lib/apt-clone/dpkg-status dist-upgrade

I have the -proposed repository enabled and pinned to -1 to make apt not use it, and the upgrade fails as in the bug report.

Pinning the binaries of the fpc source package in proposed to 500 (reenabling them) makes the upgrade work.

So, point 1 is verified. It's highly likely that applies to point 2 as well, but I can't check that atm.

[Brian Murray (brian-murray)]

I've downloaded the VarLogDistupgradeAptclone file in this bug report and restored it on an Ubuntu 16.04 system. I then ran do-release-upgrade without -proposed enabled and the upgrade failed to calculate. I then enabled -proposed and the upgrade path was calculated. Setting to verification-done.

[Launchpad Janitor (janitor)]

This bug was fixed in the package fpc - 3.0.4+dfsg-18ubuntu2

---------------
fpc (3.0.4+dfsg-18ubuntu2) bionic; urgency=medium

  * Remove wrong fp-units-base-3.0.4 Breaks fp-units-misc-3.0.0, this breaks
    upgrades from xenial (LP: #1786486)

 -- Julian Andres Klode <email address hidden> Wed, 29 Aug 2018 22:39:50 +0200

[Chris Halse Rogers (raof)]

The verification of the Stable Release Update for fpc has completed successfully and the package has now been released to -updates. Subsequently, the Ubuntu Stable Release Updates Team is being unsubscribed and will not receive messages about this bug report. In the event that you encounter a regression using the package from -updates please report a new bug using ubuntu-bug and tag the bug report regression-update so we can easily find any regressions.