[Bug 1807043] Re: when rewriting sources.list ubuntu-release-upgrader doesn't check to see if new release is available

[Brian Murray]

Actually the thing I wanted to test was an upgrade from Xenial to Bionic
with the dist-upgrader from -proposed. I've done that now and we can see
the following messages in /var/log/dist-upgrade/main.log:

2019-01-23 13:53:38,179 DEBUG entry 'deb-src http://ubuntu.osuosl.org/ubuntu bionic-security main restricted universe multiverse' updated to new dist
2019-01-23 13:53:38,180 DEBUG examining: 'deb http://ppa.launchpad.net/bryce/builds/ubuntu xenial main'
2019-01-23 13:53:38,180 DEBUG verifySourcesListEntry: deb http://ppa.launchpad.net/bryce/builds/ubuntu bionic main
2019-01-23 13:53:38,181 DEBUG url_downloadable: http://ppa.launchpad.net/bryce/builds/ubuntu/dists/bionic/Release
2019-01-23 13:53:38,181 DEBUG s='http' n='ppa.launchpad.net' p='/bryce/builds/ubuntu/dists/bionic/Release' q='' f=''
2019-01-23 13:53:38,489 DEBUG error from httplib: 'HTTP Error 404: Not Found'
2019-01-23 13:53:38,490 DEBUG entry '# deb http://ppa.launchpad.net/bryce/builds/ubuntu xenial main' was disabled (no Release file)

I had to use a different PPA since xbmc one exists for Bionic and
Xenial.

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https://bugs.launchpad.net/bugs/1807043

Title:
  when rewriting sources.list ubuntu-release-upgrader doesn't check to
  see if new release is available

Status in ubuntu-release-upgrader package in Ubuntu:
  Fix Released
Status in ubuntu-release-upgrader source package in Bionic:
  Fix Committed
Status in ubuntu-release-upgrader source package in Cosmic:
  Fix Released

Bug description:
  [Impact]
  When rewriting sources.list entries the release-upgrader doesn't check to see if the distribution to which the system is being upgraded is supported by the archive / PPA. This results in the following error message:

  A problem occurred during the update. This is usually some sort of
  network problem, please check your network connection and retry.

  E:The repository 'http://ppa.launchpad.net/team-xbmc/ppa/ubuntu
  cosmic Release' does not have a Release file.

  If the release-upgrader were to actually check if the release were
  supported then that specific sources entry could be disabled and the
  upgrade may be able to proceed.

  [Test Case]
  The test case involves adding a PPA which doesn't have a release file for the release to which you are upgrading for upgrading to cosmic we can use the team-xbmc ppa.

  1) sudo add-apt-repository ppa:team-xbmc/ppa
  2) do-release-upgrade --frontend DistUpgradeViewText
  3) Observe the error message re "does not have a Release file" and the upgrade cancel.

  With the version of the release upgrader from -proposed you will
  instead see the following message: "Some third party entries in your
  sources.list were disabled.". Then the release upgrade will proceed to
  the calculation phase, you can quit the upgrade after the calculation
  and check /var/log/dist-upgrade/main.log for the following:

  DEBUG entry '# deb http://ppa.launchpad.net/team-xbmc/ppa/ubuntu
  bionic main' was disabled (no Release file)

  [Regression Potential]
  It seems like an oversight that this part of the release-upgrader never did check for Release files and that this is the right thing to do. Its possible that people who were not allowed to upgrade, because they had PPAs without support for the release to which they wanted to upgrade, are now allowed to upgrade and somehow run in to an upgrade failure e.g. a failure to calculate the upgrade. That seems better and more informative than not allowing them to upgrade at all though.

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