Release distribution upgrade failure on Wily

[Jamie S.]

lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 15.10
Release: 15.10
Codename: wily

do-release upgrade fails even with apt/sources.list.d moved out of the way to disable add-on packages

```
Fetched 2,053 kB in 6s (1,893 B/s)

Checking package manager
Reading package lists... Done
Building dependency tree
Reading state information... Done

Calculating the changes

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

Aborting
Reading package lists... Done
Building dependency tree
Reading state information... Done
```

/var/log/unattended-upgrades/unattended-upgrades.log

```
2016-09-07 12:42:53,142 INFO Initial blacklisted packages:
2016-09-07 12:42:53,143 INFO Initial whitelisted packages:
2016-09-07 12:42:53,143 INFO Starting unattended upgrades script
2016-09-07 12:42:53,143 INFO Allowed origins are: ['o=Ubuntu,a=wily-security']
2016-09-07 12:42:53,144 ERROR Lock could not be acquired (another package manager running?)
```

^Only thing running for updates was this same update and don't see another log. Ended up forcing the update manually by editing sources.list from Wily to Xenial, also /var/log/apport.log is empty.

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: ubuntu-release-upgrader-core 1:15.10.14.4
ProcVersionSignature: Ubuntu 4.2.0-42.49-generic 4.2.8-ckt12
Uname: Linux 4.2.0-42-generic x86_64
ApportVersion: 2.19.1-0ubuntu5
Architecture: amd64
CrashDB: ubuntu
Date: Wed Sep 7 12:32:06 2016
InstallationDate: Installed on 2015-11-20 (291 days ago)
InstallationMedia: Kubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
PackageArchitecture: all
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to wily on 2016-09-07 (0 days ago)

[Brian Murray (brian-murray)]

It's not enough to just move the sources.list file out of the way, you'd need to revert to the Xorg packages provided by the official Ubuntu archive instead of the PPA you are using. There is a tool called ppa-purge which will do just that.