[FFe] please merge unattended-upgrades 1.1 (main) from Debian unstable (main)

Feature Freeze Justification
============================

Latest unattended-upgrades upload fixed multiple serious issues and includes a few minor fixes which are not worth skipping.

Most notably it now runs upgrade-between-snapshots autopkgtest with updated python-apt thus regressions can block migration to release pocket and fixes frequent crashes due to using python-apt's API in a wrong way.

Changes:
 unattended-upgrades (1.1ubuntu1) bionic; urgency=medium
 .
   * Merge from Debian unstable (LP: #1764797)
     - Remaining changes:
       - unattended-upgrades: Do not automatically upgrade the development
         release of Ubuntu unless Unattended-Upgrade::DevRelease is true.
     - Dropped changes, included in Debian:
       - Rename d/NEWS.Debian to d/NEWS to have it shipped
       - Fix typo in NEWS file
       - d/rules: Exclude mypy cache from source package.
 .
 unattended-upgrades (1.1) unstable; urgency=medium
 .
   [ cgail914 ]
   * Update 50unattended-upgrades.Raspbian
     added a semi-column sign on line 86 to facilitate uncommenting the line
     for users and not end up with an error message when running
     unattended-upgrades. And make the whole file consistent.
 .
   [ Tobias Bannert ]
   * completed german translation
 .
   [ Simon McVittie ]
   * d/rules: Exclude mypy cache from source package.
 .
   [ Julian Andres Klode ]
   * Do not reuse old apt.Version objects after reopening cache (LP: #1737441)
 .
   [ Balint Reczey ]
   * Rename d/NEWS.Debian to d/NEWS to have it shipped
   * Fix typo in NEWS file
   * Add missing semicolon to commented-out Remove-Unused-Kernel-Packages option
   * Set UnattendedUpgradesCache.allowed_origins before calling
     apt.Cache.__init__()
   * Find package candidates to adjust sweeping through all packages only once.
     Later reuse the list candidates and filter out packages installed in the
     meantime. Thanks to Julian Andres Klode for the original patch
   * Use updated python-apt in upgrade-between-snapshots test
   * upgrade-between-snapshots: Mount /proc, too, in the chroot.
     Also clean up chroot properly on exit.
   * upgrade-between-snapshots: Use http_proxy environment variable in chroot,
     too
   * upgrade-between-snapshots: Remove packages installed as the side-effect of
     updating apt and python-apt
   * Ignore errors from compiling backported packages
   * Make is_autoremove_valid() nondestructive.
     Also fix autoremoval of packages when one package can't be removed and
     keeps back other package removals due to missing cache.clear()
   * Fix tracking removed packages
   * Suggest default-mta | mail-transport-agent to keep Lintian happy
 .
   [ Michael Vogt ]
   * unattanded-upgrades: refactor get_candidates_to_adjust() to
     adjust_candidates()