Always explain why packages are held back in logs even without debugging enabled

[Balint Reczey]

[Impact]

 * Unattended-upgrades' log does not contain information about why held packages are kept back unless debugging is enabled. Users should be explained why packages are kept back to let them easily resolve the issues keeping the packages from being upgraded.

[Launchpad Janitor (janitor)]

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

[Bill Miller (wbmilleriii)]

I'd prefer that the message be suppressed when the packages in question are pinned. In this case, not updating them is the desired action, and errors/warnings are not appropriate.

[Launchpad Janitor (janitor)]

This bug was fixed in the package unattended-upgrades - 1.18

---------------
unattended-upgrades (1.18) experimental; urgency=medium

  [ louib ]
  * Update blacklist translations
  * Fix syntax in template conf files

  [ Balint Reczey ]
  * Keep mypy 0.761 happy
  * test: Create empty dirs to save kept packages list to them
  * Log explanation about kept back packages (LP: #1850964)
    (Closes: #945837, #903875)
  * Use GitHub Actions for CI instead of Travis.
    Run tests in Ubuntu Focal release because older releases don't have the
    needed python-apt version.
  * debian/tests/common-functions: Use backported python-apt from a PPA on Eoan
  * debian/tests: Skip upgrade-between-snapshots test.
    Python-apt's version is sid is too low for unattended-upgrades to work.
  * Use apt_pkg.Hashes instead of deprecated apt_pkg.md5sum()
  * autopkgtest: Skip upgrate-all-security in sid because buster can't be tested
  * Make allowed_origins, blacklist and whitelist attributes of
    UnattendedUpgradesCache
  * Make strict_whitelist attribute of UnattendedUpgradesCache
  * Apply pinning to disable not allowed origins and honor blacklist/whitelist.
    This makes candidate adjustments obsolete, since apt's resolver would pick
    candidates only from allowed origins by itself unless local pinning
    configuration overrides that.
  * Rely fully on pinning to disable allowed origins and stop adjusting
    candidates.
  * Drop Unattended-Upgrade::Allow-downgrade since now pinning is honored and
    downgrades are allowed for package versions with priority >= 1000.
    (Closes: #905877, #919046, #768087, #946491) (LP: #1251228, #1434115)
  * Don't ignore allowed origin when the package's priority is < 100.
    This used to be the way of honoring the priority, but now this special case
    prevents the package from showing up as a package kept back.
  * Assume frontend locking to be supported.
    Python3-apt (>= 1.9.6~) is required which supports the frontend locking API

 -- Balint Reczey <email address hidden> Tue, 25 Feb 2020 19:28:13 +0100

[Martin Konôpka (martin.konopka)]

I see this annoying bug on a quite recently installed ubuntu 20.04.3 LTS (GNU/Linux 5.11.0-36-generic x86_64):

1 updates could not be installed automatically. For more details,
see /var/log/unattended-upgrades/unattended-upgrades.log