[Bug 1668847] Re: live-build: handle downgrade of package priority in -updates pocket

[Andy Whitcroft]

Hello Steve, or anyone else affected,

Accepted live-build into xenial-proposed. The package will build now and
be available at https://launchpad.net/ubuntu/+source/live-
build/3.0~a57-1ubuntu25.2 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 to verification-done. If it does not fix the
bug for you, please add a comment stating that, and change the tag to
verification-failed.  In either case, details of your testing will help
us make a better decision.

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

** Changed in: live-build (Ubuntu Xenial)
       Status: New => Fix Committed

** Tags added: verification-needed

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https://bugs.launchpad.net/bugs/1668847

Title:
  live-build: handle downgrade of package priority in -updates pocket

Status in live-build package in Ubuntu:
  Fix Released
Status in live-build source package in Xenial:
  Fix Committed

Bug description:
  On rare occasions, we may wish to remove a package from the set of
  required packages post-release.  It is possible to have a binary
  package with a different priority in the release pocket vs. the
  updates pocket, but debootstrap only ever operates against a single
  pocket; so while debootstrapping, the demotion is invisible and a
  package which is Priority: required in the release, but Priority:
  important or lower in -updates, remains installed even if we're trying
  to do a minbase bootstrap.

  Since changing debootstrap to look at multiple pockets would be
  extremely non-trivial, a simpler solution is to have live-build, the
  common code that wraps debootstrap for any of our official image
  builds, identify the demotions and try to remove them from the target
  environment.

  [SRU Justification]
  This is a change in the behavior of live-build which is only relevant to already-stable releases.  We specifically have packages we would like to demote from Required in xenial; this change is required in order for those demotions to be effective.

  [Test case]
  Build an ubuntu-base image with -proposed enabled.  Verify that it builds successfully, and that the locales package is not included in the image.

  [Regression potential]
  This patch takes pains to ensure that only demoted packages are removed from the target chroot, and only if no other installed packages depend on them.  Since the only package which currently has Priority: required in xenial but Priority: important in xenial-updates is locales, there should be minimal risk of regression outside the test path.

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