Add 'return 0' to the cleanup

We may not have a stash when running this, which will cause issues. This
gets around that.
Let us run these tests from a script more easily
Changed the pre-commit hook to use python

Lets us do some cooler things in a slightly nicer way. And we do expect
you to have two pythons.
Changes to python pre-commit hook
Don't test the hooks when we modify them

That should be done manually, not at commit time.