Ubuntu 18.04 upgrade from 16.04 failed

[Srinivas Anumala]

I have removed all packages and retried upgrade. Its failing with same reason "Could not calculate upgrade"

What else is missing here ?? :(

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubuntu-release-upgrader-core 1:16.04.25
ProcVersionSignature: Ubuntu 4.15.0-29.31~16.04.1-generic 4.15.18
Uname: Linux 4.15.0-29-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia_drm nvidia_modeset nvidia
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Sun Jul 29 11:55:29 2018
InstallationDate: Installed on 2018-04-22 (98 days ago)
InstallationMedia: Ubuntu 16.04.4 LTS "Xenial Xerus" - Release amd64 (20180228)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to xenial on 2018-07-29 (0 days ago)
VarLogDistupgradeTermlog:

mtime.conffile..etc.update-manager.release-upgrades: 2018-07-28T20:03:58.267947

[Srinivas Anumala (anumalasri)]

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

User might have installed other Softwares, as per their need.

It would be great, to display details what Softwares are causing Ubuntu Release upgrade.

Can Ubuntu be able to remove or upgrade them at back-end and notify user accordingly ??