unable to upgrade to 16.04 - could not calculate changes

[Rained23]

I wanted to update to 16.04, its give error with "Could not calculate changes.

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: ubuntu-release-upgrader-core 1:15.10.14.4
ProcVersionSignature: Ubuntu 4.2.0-35.40-generic 4.2.8-ckt5
Uname: Linux 4.2.0-35-generic x86_64
ApportVersion: 2.19.1-0ubuntu5
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: Unity
Date: Wed Apr 6 10:22:12 2016
InstallationDate: Installed on 2016-03-21 (16 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to wily on 2016-04-06 (0 days ago)
VarLogDistupgradeTermlog:

[Brian Murray (brian-murray)]

Reviewing the files from your upgrade attempt you seem to have enabled a PPA that provides Xorg packages. This will prevent the upgrade as that PPA contains different versions of packages essential to Ubuntu. The page, https://launchpad.net/~xorg-edgers/+archive/ppa, contains details on to how to revert to the official Xorg packages for the xorg-edgers PPA. Instructions for reverting to official Xorg packages should be similar for the PPA that you have enabled.

[Rained23 (rained23)]

Hi,

I resolved my issue by using ppa purge on ppa:oibaf/graphics-drivers.

Reinstalling default Xorg solved the upgrade issue.