Upgrade scripts to Python 3

**Type of issue**: other enhancement
**Impact**: no functional change
**Development Phase**: proposal

There are a few Python scripts in this repo that use *Python 2*. This isn't installed by default in most repos anymore and I think it's even being removed from some. I don't really want to have my system unless some scripts accidentally use it - a lot of Python code (including these scripts!) just runs `python` which is sometimes Python 2 and sometimes Python 3, so you don't know which one it wants.

Fortunately the scripts seem to be quite small so it should be easy to update them.

See also #2629 - I also ran into this error and it's quite annoying because it doesn't say where the error originates from. Even worse, Ubuntu suggests installing `python-is-python3` which I'm guessing based on the name will just link `python` to `python3` and things will break even more.

Start by locating the repository's Python scripts and checking which invoke Python 2 or the ambiguous `python` command. Update the affected scripts for Python 3 and verify that they run without requiring Python 2; the issue does not name specific files or tests.

Written by the indexing model from the issue text.