postrm is in gpr 0.15deb-2.
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 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 | #!/bin/sh -e
W=/usr/lib/gpr/lpr.wrapper
D=/usr/bin/lpr.not.gpr
L=/usr/bin/lpr
if [ remove = "$1" ]; then
    #act only if diversion is there
    if  dpkg-divert --list gpr | grep -q $D ; then
        #remove the link?
	if [  -L $L ] && find $L -printf '%l' | egrep -q "$W|$D" ; then
		rm $L
	fi
        #remove the diversion?
	if [ -e  $L ] ; then 
	    echo gpr problem: $L exists, cannot remove diversion 1>&2
	    exit 5
	else
	    dpkg-divert --package gpr --remove --rename \
		--divert $D $L 
	fi
    fi
fi
# Automatically added by dh_installmenu
if [ -x "`which update-menus 2>/dev/null`" ]; then update-menus ; fi
# End automatically added section
# Automatically added by dh_installdebconf
if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
	. /usr/share/debconf/confmodule
	db_purge
fi
# End automatically added section
 |