preinst is in python3-plainbox 0.5.3-2.
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  | #! /bin/sh
# Pre-install script for ‘python3-plainbox’.
#
# Manpage: ‘dh_installdeb(1)’
set -e
# Summary of ways this script can be called:
#   * <new-preinst> install
#   * <new-preinst> install <old-version>
#   * <new-preinst> upgrade <old-version>
#   * <old-preinst> abort-upgrade <new-version>
# For details, see the Debian Policy §6.5 in the ‘debian-policy’ package
# or on the web at <URL:http://www.debian.org/doc/debian-policy/>.
action="$1"
case "$action" in
    upgrade)
        data_dir="/usr/lib/python3/dist-packages/plainbox/data"
        if [ -d "$data_dir" ] && [ ! -L "$data_dir" ] ; then
            # The ‘data’ location should be platform-independent.
            # The new package will replace the directory with a symlink.
            rm -rf "$data_dir"
        fi
        testdata_dir="/usr/lib/python3/dist-packages/plainbox/test-data"
        if [ -d "$testdata_dir" ] && [ ! -L "$testdata_dir" ] ; then
            # The ‘data’ location should be platform-independent.
            # The new package will replace the directory with a symlink.
            rm -rf "$testdata_dir"
        fi
        ;;
    install|abort-upgrade)
        ;;
    *)
        printf "preinst called with unknown action ‘%s’\n" "$action" >&2
        exit 1
        ;;
esac
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