package grub-efi-amd64-signed 1.93.7+2.02-2ubuntu8.6 failed to install/upgrade: installed grub-efi-amd64-signed package post-installation script subprocess returned error exit status 1

bug while updatingg

ProblemType: Package
DistroRelease: Ubuntu 18.04
Package: grub-efi-amd64-signed 1.93.7+2.02-2ubuntu8.6
ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17
Uname: Linux 4.15.0-20-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.4
Architecture: amd64
Date: Sun Oct 14 11:44:18 2018
ErrorMessage: installed grub-efi-amd64-signed package post-installation script subprocess returned error exit status 1
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
 apt 1.6.3ubuntu0.1
SourcePackage: grub2-signed
Title: package grub-efi-amd64-signed 1.93.7+2.02-2ubuntu8.6 failed to install/upgrade: installed grub-efi-amd64-signed package post-installation script subprocess returned error exit status 1
UpgradeStatus: No upgrade log present (probably fresh install)