package grub-efi-amd64 2.02~beta2-36ubuntu3.11 failed to install/upgrade: subprocess installed post-installation script returned error exit status 2

[Vasilis Lemonidis]

It seems to have started happening after denying from a script to disable safe booting. The reason why I did this was that nvidia drivers malfunctioned otherwise. I do not know if this is the real cause, but I observed it after this action. Also, in conjuction with this bug, I have observed high cpu usage from apport, before the above error appearing on the screen.

ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: grub-efi-amd64 2.02~beta2-36ubuntu3.11
ProcVersionSignature: Ubuntu 4.4.0-79.100-generic 4.4.67
Uname: Linux 4.4.0-79-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia_drm nvidia_modeset nvidia
ApportVersion: 2.20.1-0ubuntu2.6
AptOrdering:
 grub-efi-amd64: Configure
 grub-efi-amd64-signed: Configure
 NULL: ConfigurePending
Architecture: amd64
Date: Sun May 21 02:24:24 2017
DpkgTerminalLog:
 Setting up grub-efi-amd64 (2.02~beta2-36ubuntu3.10) ...
 /var/lib/dpkg/info/grub-efi-amd64.postinst: line 703: syntax error near unexpected token `fi'
 dpkg: error processing package grub-efi-amd64 (--configure):
  subprocess installed post-installation script returned error exit status 2
DuplicateSignature:
 package:grub-efi-amd64:2.02~beta2-36ubuntu3.11
 Setting up grub-efi-amd64 (2.02~beta2-36ubuntu3.10) ...
 /var/lib/dpkg/info/grub-efi-amd64.postinst: line 703: syntax error near unexpected token `fi'
 dpkg: error processing package grub-efi-amd64 (--configure):
  subprocess installed post-installation script returned error exit status 2
ErrorMessage: subprocess installed post-installation script returned error exit status 2
InstallationDate: Installed on 2016-06-06 (353 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
ProcCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-79-generic root=UUID=251db89b-1194-496c-addb-746959682b8f ro quiet splash pcie_aspm=force acpi_osi= vt.handoff=7
RelatedPackageVersions:
 dpkg 1.18.4ubuntu1.2
 apt 1.2.20
SourcePackage: grub2
Title: package grub-efi-amd64 2.02~beta2-36ubuntu3.11 failed to install/upgrade: subprocess installed post-installation script returned error exit status 2
UpgradeStatus: No upgrade log present (probably fresh install)