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

[Brian Murray]

I tested an upgrade from Xenial to Bionic with some ROS packages
installed from their archive. With the version of ubuntu-release-
upgrader from bionic-proposed I received a more informative error
message.

An unresolvable problem occurred while calculating the upgrade.

This was likely caused by: 
* Unofficial software packages not provided by Ubuntu 
Please use the tool 'ppa-purge' from the ppa-purge 
package to remove software from a Launchpad PPA and 
try the upgrade again. 

If none of this applies, then please report this bug using the 
command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal.If 
you want to investigate this yourself the log files in 
'/var/log/dist-upgrade' will contain details about the upgrade. 
Specifically, look at 'main.log' and 'apt.log'. 


Restoring original system state


Setting to verification-done.

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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:
  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:
  Test Case
  ---------
  1) add this PPA to your system 'sudo add-apt-repository ppa:oibaf/graphics-drivers'
  2) run 'sudo apt-get update; sudo apt-get dist-upgrade'
  3) try to upgrade to Cosmic
  4) Observe the following message:
  "Could not calculate the upgrade

  An unresolvable problem occurred while calculating the upgrade.

  This can be caused by:
  * Upgrading to a pre-release version of Ubuntu
  * Running the current pre-release version of Ubuntu
  * Unofficial software packages not provided by Ubuntu

  If none of this applies, then please report this bug using the
  command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal."

  With the version of the package from -proposed you should instead see
  the following in the error message:

  "If none of this applies, then please report this bug using the
  command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal. If
  you want to investigate this yourself the log files in
  '/var/log/dist-upgrade' will contain details about the upgrade.
  Specifically, look at 'main.log' and 'apt.log'."

  Regression Potential
  --------------------
  This change does end up breaking translations but the message is much more informative and lots of users have difficulty upgrading between releases which can leave them on an insecure (EoL) release of Ubuntu which is worse.

  
  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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