postrm is in glance-common 2012.1.3+stable~20120821-120fcf-0ubuntu1.5.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 | #!/bin/sh
set -e
case $1 in
	purge)
		if (which deluser && getent passwd glance) > /dev/null 2>&1; then
			deluser --system --quiet --backup-to /var/lib glance
		fi	
		if (which delgroup && getent group glance) > /dev/null 2>&1; then
			delgroup --system --quiet glance
		fi
		;;
esac
 |