Cannot remove if user maas does not exist

[Kevin Dalley]

If the user maas does not exist, then the package maas-cluster-controller cannot be removed.

Here is output from an attempt at removing maas-cluster-controller

kevin@nereocystis:~$ sudo aptitude purge maas-cluster-controller
[sudo] password for kevin:
The following packages will be REMOVED:
  maas-cluster-controller{p}
0 packages upgraded, 0 newly installed, 1 to remove and 0 not upgraded.
Need to get 0 B of archives. After unpacking 0 B will be used.
Do you want to continue? [Y/n/?]
(Reading database ... 612148 files and directories currently installed.)
Removing maas-cluster-controller (1.7.3+bzr3363-0ubuntu2) ...
Purging configuration files for maas-cluster-controller (1.7.3+bzr3363-0ubuntu2) ...
id: maas: no such user
dpkg: error processing package maas-cluster-controller (--purge):
 subprocess installed post-removal script returned error exit status 1
Errors were encountered while processing:
 maas-cluster-controller
E: Sub-process /usr/bin/dpkg returned an error code (1)
Failed to perform requested operation on package. Trying to recover:

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: maas-cluster-controller 1.7.3+bzr3363-0ubuntu2
ProcVersionSignature: Ubuntu 3.19.0-15.15-generic 3.19.3
Uname: Linux 3.19.0-15-generic x86_64
ApportVersion: 2.17.2-0ubuntu1
Architecture: amd64
CurrentDesktop: Unity
Date: Wed Apr 29 20:54:33 2015
InstallationDate: Installed on 2013-06-02 (696 days ago)
InstallationMedia: Ubuntu 13.04 "Raring Ringtail" - Release amd64 (20130424)
PackageArchitecture: all
SourcePackage: maas
UpgradeStatus: No upgrade log present (probably fresh install)
modified.conffile..etc.maas.maas.cluster.conf: [inaccessible: [Errno 13] Permission denied: '/etc/maas/maas_cluster.conf']
modified.conffile..etc.sudoers.d.99.maas.sudoers: [inaccessible: [Errno 13] Permission denied: '/etc/sudoers.d/99-maas-sudoers']
upstart.isc-dhcp-server.override: manual