grub fails to add boot entries if python3-apt is missing

[Dalton Durst]

In mantic and noble, when update-grub is run without python3-apt installed, the following output is generated:

    Sourcing file `/etc/default/grub'
    Generating grub configuration file ...
    Traceback (most recent call last):
    File "/usr/lib/grub/grub-sort-version", line 4, in <module>
        import apt_pkg
    ModuleNotFoundError: No module named 'apt_pkg'
    Traceback (most recent call last):
    File "/usr/lib/grub/grub-sort-version", line 4, in <module>
        import apt_pkg
    ModuleNotFoundError: No module named 'apt_pkg'
    Traceback (most recent call last):
    File "/usr/lib/grub/grub-sort-version", line 4, in <module>
        import apt_pkg
    ModuleNotFoundError: No module named 'apt_pkg'
    Adding boot menu entry for UEFI Firmware Settings ...
    done

When this occurs, no Linux boot options are added to the GRUB config.

grub-sort-version was added to the grub-common binary package in 2.12~rc1-10ubuntu2. It is a python script which sorts the kernel versions via Debian rules using apt_pkg. The grub package was updated to depend on python3 so this script could run. However, the script also depends on python3-apt.

Either grub-sort-version should be changed not to depend on python3-apt (or fail gracefully when it's missing) or python3-apt should be added to the dependencies of grub-common.

[Julian Andres Klode (juliank)]

The whole thing is a bit annoying but it was nicer than forking dpkg --compare-versions for each pair. I'm not sure how you ended up with a system without python3-apt, it should be pulled in via ubuntu-minimal->uuntu-advantage-tools already and you can't just go remove those packages and still pretend you have a supported system.

[Mate Kukri (mkukri)]

Can anyone think of a good reason for GRUB to be installed on a system without python3-apt?

If no such scenario comes up, I'll add python3-apt to grub-common's Deopends: in the next upload.

[Dalton Durst (universalsuperbox)]

Hi Julian, Mate,

I think adding python3-apt to the Depends of grub-common is a good solution. This issue is not urgent and is easily worked around, so waiting for the next upload is absolutely fine. Thank you!

As for how I got a system into this state... It never had python3-apt installed. I built the system by running 'debootstrap --variant=minbase noble noble http://archive.ubuntu.com/ubuntu gutsy' and added exactly the packages I needed. I won't pretend that I've created a system that I can go to libera.chat #ubuntu and ask for help with, but as in Debian, the only packages that a binary control file can assume as installed are those in the 'Priority: Required' set. I think it is worth keeping that usecase available, and if you say that I need to do more work to keep it that way I'm fine with putting in the effort.

[Mate Kukri (mkukri)]

This will be resolved by 2.12 final, but quick fix to unblock https://bugs.launchpad.net/cloud-images/+bug/2052743

[Launchpad Janitor (janitor)]

This bug was fixed in the package grub2 - 2.12~rc1-12ubuntu5

---------------
grub2 (2.12~rc1-12ubuntu5) noble; urgency=medium

  * d/control: Add python3-apt to Depends of grub-common (LP: #2048953)

 -- Mate Kukri <email address hidden> Fri, 09 Feb 2024 13:23:36 +0000