postrm is in akonadi-backend-mysql 4:17.12.3-0ubuntu3.
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 | #!/bin/sh
set -e
# Automatically added by dh_apparmor/2.12-4ubuntu4
if [ "$1" = "purge" ] && ! [ -e "/etc/apparmor.d/usr.sbin.mysqld-akonadi" ] ; then
    rm -f "/etc/apparmor.d/disable/usr.sbin.mysqld-akonadi" || true
    rm -f "/etc/apparmor.d/force-complain/usr.sbin.mysqld-akonadi" || true
    rm -f "/etc/apparmor.d/local/usr.sbin.mysqld-akonadi" || true
    rmdir /etc/apparmor.d/disable 2>/dev/null || true
    rmdir /etc/apparmor.d/local   2>/dev/null || true
    rmdir /etc/apparmor.d         2>/dev/null || true
fi
# End automatically added section
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