package grub-efi-amd64 2.02~beta2-29ubuntu0.3 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1

[Stan Schymanski]

I switched from Legacy to EFI boot using a live CD and boot-repair. The system booted fine, but when running a software update, an error message appeared, asking me to report a bug, so here it is.

Ubuntu Gnome 15.10

ProblemType: Package
DistroRelease: Ubuntu 15.10
Package: grub-efi-amd64 2.02~beta2-29ubuntu0.3
ProcVersionSignature: Ubuntu 4.2.0-25.30-generic 4.2.6
Uname: Linux 4.2.0-25-generic x86_64
ApportVersion: 2.19.1-0ubuntu5
Architecture: amd64
Date: Wed Jan 27 23:47:48 2016
Df:

ErrorMessage: subprocess installed post-installation script returned error exit status 1
InstallationDate: Installed on 2016-01-26 (1 days ago)
InstallationMedia: Ubuntu-GNOME 15.10 "Wily Werewolf" - Release amd64 (20151021)
InvalidGrubScript: /etc/grub.d/25_custom
ProcCmdLine: BOOT_IMAGE=/vmlinuz-4.2.0-25-generic.efi.signed root=/dev/mapper/sysvg-lvroot ro quiet splash vt.handoff=7
RelatedPackageVersions:
 dpkg 1.18.2ubuntu5.1
 apt 1.0.10.2ubuntu1
SourcePackage: grub2
Title: package grub-efi-amd64 2.02~beta2-29ubuntu0.3 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1
UpgradeStatus: No upgrade log present (probably fresh install)

[Phillip Susi (psusi)]

You still have the bios version of grub installed. You need to remove grub-pc and install grub-efi instead.