prerm is in python3.4-dbg 3.4.0-2ubuntu1.
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
set -e
remove_bytecode()
{
    pkg=$1
    max=$(LANG=C LC_ALL=C xargs --show-limits < /dev/null 2>&1 | awk '/Maximum/ {print int($NF / 4)}')
    dpkg -L $pkg \
	| awk -F/ 'BEGIN {OFS="/"} /\.py$/ {$NF=sprintf("__pycache__/%s.*.py[co]", substr($NF,1,length($NF)-3)); print}' \
	| xargs --max-chars=$max echo \
	| while read files; do rm -f $files; done
    if [ -d /usr/bin/__pycache__ ]; then
	rmdir --ignore-fail-on-non-empty /usr/bin/__pycache__
    fi
}
case "$1" in
    remove)
	remove_bytecode libpython3.4-dbg
        ;;
    upgrade)
	remove_bytecode libpython3.4-dbg
        ;;
    deconfigure)
        ;;
    failed-upgrade)
        ;;
    *)
        echo "prerm called with unknown argument \`$1'" >&2
        exit 1
    ;;
esac
 |