/usr/share/python/runtime.d/python-gst0.10-dev.rtupdate is in python-gst0.10-dev 0.10.22-3.
This file is owned by root:root, with mode 0o644.
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 44 45 | #!/bin/sh
# this script updates symlinks to pkg-config files after a Python default
# runtime change
if [ "$#" != 3 ]; then
    echo "Usage: $0 {pre-rtupdate|post-rtupdate|rtupdate} <oldruntime> <newruntime>" >&2
    exit 1
fi
action="$1"
oldruntime="$2"
newruntime="$3"
this="python-gst0.10"
pc_files() {
    runtime="$1"
    dpkg -L "$this" | sed -n -e "s#^/usr/lib/pkgconfig/$runtime/##p"
}
case "$action" in
  pre-rtupdate)
  ;;
  post-rtupdate)
  ;;
  rtupdate)
    echo "Updating *.pc symlinks for $this..."
    cd /usr/lib/pkgconfig
    for f in $(pc_files $oldruntime); do
        rm -f "$f"
    done
    for f in $(pc_files $newruntime); do
        ln -s "$newruntime/$f"
    done
  ;;
  *)
    echo "$0 called with unknown argument \`$action'" >&2
    exit 0
  ;;
esac
 |