package grub-pc 2.02-2ubuntu8.23 failed to install/upgrade: installed grub-pc package post-installation script subprocess returned error exit status 1

[Rajnish R Lal]

got this error while upgrading from 16.04 to 18.04

ProblemType: Package
DistroRelease: Ubuntu 18.04
Package: grub-pc 2.02-2ubuntu8.23
ProcVersionSignature: Ubuntu 4.15.0-142.146~16.04.1-generic 4.15.18
Uname: Linux 4.15.0-142-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.26
Architecture: amd64
Date: Tue Oct 12 21:39:59 2021
ErrorMessage: installed grub-pc package post-installation script subprocess returned error exit status 1
InstallationDate: Installed on 2019-09-06 (767 days ago)
InstallationMedia: Ubuntu 16.04.4 LTS "Xenial Xerus" - Release amd64 (20180228)
ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.15.0-142-generic root=UUID=ae833b83-c43a-4ac5-a12a-7f93221f9b57 ro net.ifnames=0 biosdedvname=0 quiet splash
Python3Details: /usr/bin/python3.6, Python 3.6.9, python3-minimal, 3.6.7-1~18.04
PythonDetails: /usr/bin/python2.7, Python 2.7.17, python-minimal, 2.7.15~rc1-1
RelatedPackageVersions:
 dpkg 1.19.0.5ubuntu2.3
 apt 1.6.14
SourcePackage: grub2
Title: package grub-pc 2.02-2ubuntu8.23 failed to install/upgrade: installed grub-pc package post-installation script subprocess returned error exit status 1
UpgradeStatus: Upgraded to bionic on 2021-10-12 (0 days ago)