package sendmail-base 8.15.2-11 failed to install/upgrade: installed sendmail-base package post-installation script subprocess returned error exit status 255

during upgrade to ubuntu 2018 October release

ProblemType: Package
DistroRelease: Ubuntu 18.10
Package: sendmail-base 8.15.2-11
ProcVersionSignature: Ubuntu 4.18.0-10.11-generic 4.18.12
Uname: Linux 4.18.0-10-generic x86_64
ApportVersion: 2.20.10-0ubuntu13
Architecture: amd64
Date: Sat Oct 20 05:59:13 2018
ErrorMessage: installed sendmail-base package post-installation script subprocess returned error exit status 255
InstallationDate: Installed on 2014-03-28 (1666 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Beta amd64 (20140326)
PackageArchitecture: all
Python3Details: /usr/bin/python3.6, Python 3.6.7rc1, python3-minimal, 3.6.6-1
PythonDetails: /usr/bin/python2.7, Python 2.7.15+, python-minimal, 2.7.15-3
RelatedPackageVersions:
 dpkg 1.19.0.5ubuntu5
 apt 1.7.0
SourcePackage: sendmail
Title: package sendmail-base 8.15.2-11 failed to install/upgrade: installed sendmail-base package post-installation script subprocess returned error exit status 255
UpgradeStatus: Upgraded to cosmic on 2018-10-20 (0 days ago)