package fail2ban 0.11.1-1 failed to install/upgrade: conffile difference visualizer subprocess returned error exit status 127

Upgrading from 18.04 to 20

ProblemType: Package
DistroRelease: Ubuntu 20.04
Package: fail2ban 0.11.1-1
ProcVersionSignature: Ubuntu 4.15.0-101.102-generic 4.15.18
Uname: Linux 4.15.0-101-generic x86_64
ApportVersion: 2.20.11-0ubuntu27
Architecture: amd64
CasperMD5CheckResult: skip
Date: Wed May 27 22:48:45 2020
ErrorMessage: conffile difference visualizer subprocess returned error exit status 127
InstallationDate: Installed on 2020-05-20 (7 days ago)
InstallationMedia: Ubuntu-Server 18.04.4 LTS "Bionic Beaver" - Release amd64 (20200203.1)
PackageArchitecture: all
Python3Details: /usr/bin/python3.8, Python 3.8.2, python3-minimal, 3.8.2-0ubuntu2
PythonDetails: /usr/bin/python2.7, Python 2.7.18rc1, python-is-python2, 2.7.17-4
RelatedPackageVersions:
 dpkg 1.19.7ubuntu3
 apt 2.0.2ubuntu0.1
SourcePackage: fail2ban
Title: package fail2ban 0.11.1-1 failed to install/upgrade: conffile difference visualizer subprocess returned error exit status 127
UpgradeStatus: Upgraded to focal on 2020-05-27 (0 days ago)
modified.conffile..etc.fail2ban.jail.conf: [modified]
mtime.conffile..etc.fail2ban.jail.conf: 2020-05-25T00:18:23.658162