Huh, that's actually weird that the "exisisting command line interface" (quotes because it was added as a test) isn't official. I've found it to be convinient as a newcomer to the cpython codebase. 

> What is unusual, I think, for a CLI test function is that it requires a passed in argument

git blame shows the commit hash is 095668914c3, which is for bpo: https://bugs.python.org/issue18538 "python -m dis now uses argparse". The Misc/HISTORY file references the change in section "What's New in Python 3.4.0 Alpha 3?"

Regardless of the cli being official, personally I think, it's a good feature to add. But also, maybe I should start a discussion in python-ideas about making it official?