package grub-pc 2.04-1ubuntu12 failed to install/upgrade: installed grub-pc package post-installation script subprocess returned error exit status 1

[Michael Ferris]

This happened immediately after restart following upgrade from 19.04 to 19.10 without any intervention.

ProblemType: Package
DistroRelease: Ubuntu 19.10
Package: grub-pc 2.04-1ubuntu12
Uname: Linux 4.20.0-042000-generic x86_64
ApportVersion: 2.20.11-0ubuntu8
Architecture: amd64
Date: Thu Oct 24 09:54:32 2019
ErrorMessage: installed grub-pc package post-installation script subprocess returned error exit status 1
InstallationDate: Installed on 2018-09-03 (415 days ago)
InstallationMedia: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
InvalidGrubScript: /etc/grub.d/25_custom
ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.20.0-042000-generic root=UUID=222d2c83-ad55-472d-a766-e2e14bacc688 ro quiet splash noresume vt.handoff=1
Python3Details: /usr/bin/python3.7, Python 3.7.5rc1, python3-minimal, 3.7.5-1
PythonDetails: /usr/bin/python2.7, Python 2.7.17rc1, python-minimal, 2.7.17-1
RelatedPackageVersions:
 dpkg 1.19.7ubuntu2
 apt 1.9.4
SourcePackage: grub2
Title: package grub-pc 2.04-1ubuntu12 failed to install/upgrade: installed grub-pc package post-installation script subprocess returned error exit status 1
UpgradeStatus: Upgraded to eoan on 2019-10-24 (0 days ago)

[Launchpad Janitor (janitor)]

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

[Julian Andres Klode (juliank)]

This seems to be working as intended, as the debconf frontend was unable to ask a question because the X server went away

Gdk-Message: 09:54:32.784: frontend: Fatal IO error 11 (Resource temporarily unavailable) on X server :0.

and hence the upgrade failed so it can still boot.

[Roger Zimmermann (r-zimmermann)]

The error persists after a restart.
This is not an expected bahaviour since the xserver is running then.
The failed installation is announced at every run of update manager.

Also a (re-)configuration brings up this error:

dpkg --configure -a
OR
dpkg --configure grub-pc

dpkg: error processing package grub-pc (--configure):
 installed grub-pc package post-installation script subprocess returned error exit status 1
Errors were encountered while processing:
 grub-pc