Getting error while upgrading from 16 to 18. An unresolvable problem occurred while calculating the upgrade.

[Hassan Siddique]

Getting error when I run this command. "sudo do-release-upgrade".

Reading state information... Done

Calculating the changes

Calculating the changes

Could not calculate the upgrade

An unresolvable problem occurred while calculating the upgrade.

If none of this applies, then please report this bug using the
command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal.If
you want to investigate this yourself the log files in
'/var/log/dist-upgrade' will contain details about the upgrade.
Specifically, look at 'main.log' and 'apt.log'.

Restoring original system state

Aborting
Reading package lists... Done
Building dependency tree
Reading state information... Done

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubuntu-release-upgrader-core 1:16.04.29
ProcVersionSignature: Ubuntu 4.15.0-70.79~16.04.1-generic 4.15.18
Uname: Linux 4.15.0-70-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.21
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Wed Nov 27 13:51:11 2019
InstallationDate: Installed on 2017-06-30 (879 days ago)
InstallationMedia: Ubuntu 16.04.2 LTS "Xenial Xerus" - Release amd64 (20170215.2)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to xenial on 2019-11-27 (0 days ago)