[Bug 1771387] Re: Could not calculate upgrade should suggest log location

[Launchpad Bug Tracker]

** Branch linked: lp:~brian-murray/ubuntu-release-upgrader/improve-
upgrade-failure-messages

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https://bugs.launchpad.net/bugs/1771387

Title:
  Could not calculate upgrade should suggest log location

Status in ubuntu-release-upgrader package in Ubuntu:
  In Progress

Bug description:
  Situation
  ===============

  As more-or-less usual, my attempt to upgrade from 16.04 to 18.04
  failed with "Could not calculate upgrade" error (well, one even more
  confusing and less google-able, as translated to my national
  language). Also, as usual, I found myself confused, without any
  pointers what to do next. I tried a few times, tried googling, to no
  success.

  It took me switching to LANG=C (to see more googlish error messages)
  and about 20 minutes of scanning various forums until I found
  suggestion to check /var/log/dist-upgrade

  There I found some rather cryptic remark  about unresolvable cyclic
  dependency which may be caused by held packages, which nevertheless
  inspired me to look for a way to find held packages.

  A few more minutes of googling and I found out about
       apt-mark showhold
  which nicely listed my few held packages (nvidia-304 and some related, IIRC results of driver problems I resolved 2 years ago).

  I removed those packages and now my upgrade is progressing. But whole
  experience was very unpleasant.

  Suggested changes (tiny changes but with large impact)
  ======================================================

  1. Whenever do-release-upgrade fails, it should suggest checking out /var/log/dist-upgrade.
     Simply, instead of finishing with
         "Could not calculate the upgrade.
         Unresolvable error happened."
     finish with
         "Could not calculate the upgrade.
         Unresolvable error happened.
         Technical logs of failed upgrade can be found in /var/log/dist-upgrade"

     This very sentence would save me at least 2 hours.

  2. In case upgrade calculation fails due to held or unofficial packages, either list problematic
     packages, or suggest commands which will list them. For example, my very case would be resolved
     in a minute if installer printed something like:

         Note: upgrade calculation could be caused by held packages:
            nvidia-304 nvidia-304-dev nvidia-current-updates
         (consider removing those packages temporarily to resolve the problem)

     or

         Note: upgrade calculation could be caused by held packages
         (use apt-mark showhold to list such packages on your system, and
          consider removing them temporarily to resolve the problem)

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