package sddm (not installed) failed to install/upgrade: subprocess installed post-removal script returned error exit status 1

[Jeffrey Tees]

15.04 vivid
sddm seems to have failed install from cli.
sudo apt-get install kubuntu-desktop
chose sddm (just to see how it looked) on reboot sddm failed to load (black screen)
switched to tty reconfigured to return to lightdm, purged sddm -> reboot lightdm ok.
On Unity login error occured (this one) saying sddm had failed to install

ProblemType: Package
DistroRelease: Ubuntu 15.04
Package: sddm (not installed)
ProcVersionSignature: Ubuntu 3.18.0-13.14-generic 3.18.5
Uname: Linux 3.18.0-13-generic x86_64
ApportVersion: 2.16.1-0ubuntu2
AptOrdering: sddm: Purge
Architecture: amd64
Date: Fri Feb 13 11:38:02 2015
DpkgTerminalLog:
 Removing sddm (0.11.0-0ubuntu3) ...
 Purging configuration files for sddm (0.11.0-0ubuntu3) ...
 rm: cannot remove ‘/var/run/sddm/authority’: No such file or directory
 dpkg: error processing package sddm (--purge):
  subprocess installed post-removal script returned error exit status 1
DuplicateSignature: package:sddm:(not installed):subprocess installed post-removal script returned error exit status 1
ErrorMessage: subprocess installed post-removal script returned error exit status 1
InstallationDate: Installed on 2014-10-28 (110 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20140228)
SourcePackage: sddm
Title: package sddm (not installed) failed to install/upgrade: subprocess installed post-removal script returned error exit status 1
UpgradeStatus: Upgraded to vivid on 2015-01-02 (44 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[apport hater (g112)]

This issue is caused by a simple error in the postrm script

> if [ -d /var/run/sddm ]; then rm -r /var/run/sddm/authority; fi

The directory exists, but the file does not.

Workaround:
Stop ssdm to be sure those files won't be missed.
Delete /var/run/sddm before purging the package.

[Arma1975 (arma1975)]

Thanks