package unattended-upgrades 0.90ubuntu0.9 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1

[mariam waheeb]

while upgrading to ubuntu 16.04

ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: unattended-upgrades 0.90ubuntu0.9
ProcVersionSignature: Ubuntu 4.4.0-109.132-generic 4.4.98
Uname: Linux 4.4.0-109-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.15
Architecture: amd64
Date: Mon Jan 22 12:26:16 2018
ErrorMessage: subprocess installed post-installation script returned error exit status 1
InstallationDate: Installed on 2017-09-09 (134 days ago)
InstallationMedia: Ubuntu 14.04.5 LTS "Trusty Tahr" - Release amd64 (20160803)
PackageArchitecture: all
RelatedPackageVersions:
 dpkg 1.18.4ubuntu1.3
 apt 1.2.24
SourcePackage: unattended-upgrades
Title: package unattended-upgrades 0.90ubuntu0.9 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1
UpgradeStatus: Upgraded to xenial on 2018-01-22 (0 days ago)
mtime.conffile..etc.apt.apt.conf.d.50unattended-upgrades: 2018-01-22T12:31:57.567750