package grub-efi-amd64-signed 1.66.18+2.02~beta2-36ubuntu3.18 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1

[Norman Baker]

kept reporting the same error. would not send a report.
dmesg
[97113.475416] wlp2s0: authenticate with f4:f2:6d:aa:de:2d
[97113.503654] wlp2s0: send auth to f4:f2:6d:aa:de:2d (try 1/3)
[97113.506939] wlp2s0: authenticated
[97113.509851] wlp2s0: associate with f4:f2:6d:aa:de:2d (try 1/3)
[97113.515995] wlp2s0: RX ReassocResp from f4:f2:6d:aa:de:2d (capab=0x1011 status=0 aid=4)
[97113.518174] wlp2s0: associated
[97113.518318] ath: EEPROM regdomain: 0x8348
[97113.518320] ath: EEPROM indicates we should expect a country code
[97113.518321] ath: doing EEPROM country->regdmn map search
[97113.518323] ath: country maps to regdmn code: 0x3a
[97113.518324] ath: Country alpha2 being used: US
[97113.518325] ath: Regpair used: 0x3a
[97113.518326] ath: regdomain 0x8348 dynamically updated by country IE
[97113.518600] wlp2s0: Limiting TX power to 30 (30 - 0) dBm as advertised by f4:f2:6d:aa:de:2d

ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: grub-efi-amd64-signed 1.66.18+2.02~beta2-36ubuntu3.18
ProcVersionSignature: Ubuntu 4.15.0-33.36~16.04.1-generic 4.15.18
Uname: Linux 4.15.0-33-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
Date: Thu Sep 6 22:43:00 2018
ErrorMessage: subprocess installed post-installation script returned error exit status 1
InstallationDate: Installed on 2017-08-07 (396 days ago)
InstallationMedia: Ubuntu 16.04.2 LTS "Xenial Xerus" - Release amd64 (20170215.2)
RelatedPackageVersions:
 dpkg 1.18.4ubuntu1.4
 apt 1.2.27
SourcePackage: grub2-signed
Title: package grub-efi-amd64-signed 1.66.18+2.02~beta2-36ubuntu3.18 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.