This interesting, I have never seen setcap. It seems it doesn't work with scripts (ruby, python) and if you are using JVM/mono/beam you will need to setcap the whole VM, but a very cool solution for a language like Go with binaries!
My two cents, you probably need to apply setcap in Python interpreter itself instead of the script. It shouldn't be a problem though, since you probably will use a virtualenv anyway.
Another option would be to drop privileges at runtime.
Not necessarily: