Cannot upgrade from 14.04.5 to 16.04.3

[Daniel Bidwell]

do-release-upgrade produces:

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.

Restoring original system state

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubuntu-release-upgrader-core 1:0.220.9
ProcVersionSignature: Ubuntu 4.4.0-98.121~14.04.1-generic 4.4.90
Uname: Linux 4.4.0-98-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.25
Architecture: amd64
CrashDB: ubuntu
Date: Mon Nov 13 21:17:08 2017
InstallationDate: Installed on 2012-05-21 (2002 days ago)
InstallationMedia: Ubuntu-Server 12.04 LTS "Precise Pangolin" - Release amd64 (20120424.1)
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to trusty on 2017-11-14 (0 days ago)