Ubuntu upgrade from 14.04 to 16.04 is having problems

[ishan durugkar]

When trying to upgrade Ubuntu from 14.04 to 16.04, the upgrader errors out.
Not sure why it's happening.

I am on Ubuntu 14.04.5 LTS
I want to upgrade to 16.04 LTS

To upgrade I ran the update from the UI first and when that didn't work I tried: 'sudo do-release-upgrade' from the terminal

The last few lines in the terminal when it errors out are:

Checking package manager
Reading package lists... Done
Building dependency tree
Reading state information... Done
Building data structures... Done

Calculating the changes

Calculating the changes

Could not calculate the upgrade

An unresolvable problem occurred while calculating the upgrade.

This can be caused by:
* Upgrading to a pre-release version of Ubuntu
* Running the current pre-release version of Ubuntu
* Unofficial software packages not provided by Ubuntu

If none of this applies, then please report this bug using the
command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubuntu-release-upgrader-core 1:0.220.9
ProcVersionSignature: Ubuntu 3.13.0-139.188-generic 3.13.11-ckt39
Uname: Linux 3.13.0-139-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia_drm nvidia_modeset nvidia
ApportVersion: 2.14.1-0ubuntu3.27
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Wed Jan 17 16:37:30 2018
InstallationDate: Installed on 2012-04-28 (2090 days ago)
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to trusty on 2018-01-17 (0 days ago)