Release upgrade from xenial to bionic failed.

[Vijayendra Agrawal]

In Xenial (16.04), there is no option to upgrade to next best version, it directly jumps to bionic and fails.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubuntu-release-upgrader-core 1:16.04.26
ProcVersionSignature: Ubuntu 4.4.0-141.167-generic 4.4.162
Uname: Linux 4.4.0-141-generic i686
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: i386
CrashDB: ubuntu
Date: Fri Jan 25 17:51:11 2019
InstallationDate: Installed on 2017-08-21 (521 days ago)
InstallationMedia: Ubuntu 14.04.2 LTS "Trusty Tahr" - Release i386 (20150218.1)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to xenial on 2019-01-25 (0 days ago)
VarLogDistupgradeAptclonesystemstate.tar.gz:
 Error: command ['pkexec', 'cat', '/var/log/dist-upgrade/apt-clone_system_state.tar.gz'] failed with exit code 127: polkit-agent-helper-1: error response to PolicyKit daemon: GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: No session for cookie
 Error executing command as another user: Not authorized

 This incident has been reported.