package grub-efi-amd64-signed 1.93.8+2.02-2ubuntu8.7 failed to install/upgrade: installed grub-efi-amd64-signed package post-installation script subprocess returned error exit status 1

[Melanie Bailey]

The installation interrupted in order to suggest that I report the bug. So I did.

ProblemType: Package
DistroRelease: Ubuntu 18.04
Package: grub-efi-amd64-signed 1.93.8+2.02-2ubuntu8.7
ProcVersionSignature: Ubuntu 4.4.0-138.164-generic 4.4.155
Uname: Linux 4.4.0-138-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.4
Architecture: amd64
Date: Sun Nov 4 18:55:44 2018
ErrorMessage: installed grub-efi-amd64-signed package post-installation script subprocess returned error exit status 1
InstallationDate: Installed on 2016-12-16 (688 days ago)
InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
Python3Details: /usr/bin/python3.6, Python 3.6.6, python3-minimal, 3.6.5-3ubuntu1
PythonDetails: /usr/bin/python2.7, Python 2.7.15rc1, python-minimal, 2.7.15~rc1-1
RelatedPackageVersions:
 dpkg 1.19.0.5ubuntu2.1
 apt 1.6.6
SourcePackage: grub2
Title: package grub-efi-amd64-signed 1.93.8+2.02-2ubuntu8.7 failed to install/upgrade: installed grub-efi-amd64-signed package post-installation script subprocess returned error exit status 1
UpgradeStatus: Upgraded to bionic on 2018-11-04 (0 days ago)