Update to Ubuntu 18.04 LTS fails from 16.4

[leo]

Displays:
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 16.04
Package: ubuntu-release-upgrader-core 1:16.04.25
ProcVersionSignature: Ubuntu 4.15.0-32.35~16.04.1-generic 4.15.18
Uname: Linux 4.15.0-32-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Tue Aug 14 17:57:16 2018
EcryptfsInUse: Yes
InstallationDate: Installed on 2017-10-23 (295 days ago)
InstallationMedia: Ubuntu 16.04.3 LTS "Xenial Xerus" - Release amd64 (20170801)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to xenial on 2018-08-14 (0 days ago)
VarLogDistupgradeTermlog:

[Brian Murray (brian-murray)]

You still have the vim-common package installed which is causing a failure too.

vim-common 2:8.1.0280-0york1~16.04 0

xxd might also be an issue.