package lightdm 1.10.5-0ubuntu1 failed to install/upgrade: subprocess installed post-removal script returned error exit status 1

[Lewis]

insert stuff here

ProblemType: Package
DistroRelease: Ubuntu 14.04
Package: lightdm 1.10.5-0ubuntu1
ProcVersionSignature: Ubuntu 3.13.0-46.79-generic 3.13.11-ckt15
Uname: Linux 3.13.0-46-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.7
Architecture: amd64
Date: Mon Apr 6 13:09:21 2015
DuplicateSignature: package:lightdm:1.10.5-0ubuntu1:subprocess installed post-removal script returned error exit status 1
ErrorMessage: subprocess installed post-removal script returned error exit status 1
InstallationDate: Installed on 2015-03-03 (33 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
LightdmConfig:
 [SeatDefaults]
 greeter-session=unity-greeter
 user-session=ubuntu
SourcePackage: lightdm
Title: package lightdm 1.10.5-0ubuntu1 failed to install/upgrade: subprocess installed post-removal script returned error exit status 1
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

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