preinst is in festival 1:2.4~release-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 34 35 36 37 38 39 40 41 42 43 | #!/bin/sh
set -e
# Remove a no-longer used conffile
rm_conffile() {
    PKGNAME="$1"
    CONFFILE="$2"
    if [ -e "$CONFFILE" ]; then
	md5sum="`md5sum \"$CONFFILE\" | sed -e \"s/ .*//\"`"
	old_md5sum="`dpkg-query -W -f='${Conffiles}' $PKGNAME | sed -n -e \"\\\\' $CONFFILE'{s/ obsolete$//;s/.* //p}\"`"
        if [ "$md5sum" != "$old_md5sum" ]; then
            echo "Obsolete conffile $CONFFILE has been modified by you."
            echo "Saving as $CONFFILE.dpkg-bak ..."
            mv -f "$CONFFILE" "$CONFFILE".dpkg-bak
        else
            echo "Removing obsolete conffile $CONFFILE ..."
            rm -f "$CONFFILE"
        fi
    fi
}
case "$1" in
install|upgrade)
    if dpkg --compare-versions "$2" le 1.96~beta-6; then
        rm_conffile festival "/etc/init.d/festival"
	[ -e "/etc/init.d/festival.dpkg-bak" ] && chmod a-x /etc/init.d/festival.dpkg-bak
        rm_conffile festival "/etc/festival.scm"
        rm_conffile festival "/etc/default/festival"
    fi
esac
# Automatically added by dh_installcatalogs
if test -f /etc/sgml/festival.cat -a "(" "$1" = "upgrade" -o "$1" = "install" -a -n "$2" ")" && 
		! dpkg-query -S /etc/sgml/festival.cat >/dev/null 2>&1; then
	# If the dpkg-query command returns non-zero, the central catalog is
	# not owned by any package. This is due to an old behaviour of
	# debhelper. Now that file becomes a conffile. In order to avoid a
	# question during installation, we remove the old non-conffile.
	mv /etc/sgml/festival.cat /etc/sgml/festival.cat.old
fi
# End automatically added section
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