Upgrade to Bionic from Xenial is not completing

[John Troll]

I am unable to update from 16.04 to 18.04, getting the "Could not calculate the upgrade" error. and have attempted to remove all launchpad related PPAs. I am running Ubuntu 16.04 LTS.

Not sure if this is related to a CUDA install I tried to do some time ago that never really worked.

Full Error:

Could not calculate the upgrade

An unresolvable problem occurred while calculating the upgrade.

 This was likely caused by:
 * Unofficial software packages not provided by Ubuntu
Please use the tool 'ppa-purge' from the ppa-purge
package to remove software from a Launchpad PPA and
try the upgrade again.

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'.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubuntu-release-upgrader-core 1:16.04.26
ProcVersionSignature: Ubuntu 4.15.0-45.48~16.04.1-generic 4.15.18
Uname: Linux 4.15.0-45-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Wed Feb 20 11:02:39 2019
EcryptfsInUse: Yes
InstallationDate: Installed on 2018-04-03 (323 days ago)
InstallationMedia: Ubuntu 16.04.4 LTS "Xenial Xerus" - Release amd64 (20180228)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to xenial on 2019-02-20 (0 days ago)
VarLogDistupgradeTermlog:

mtime.conffile..etc.update-manager.release-upgrades: 2019-02-20T08:58:57.640892

[John Troll (jtroll)]

So does this mean that for some people with ROS, they must uninstall ROS in order to upgrade Ubuntu?