Fix broken `list branches` functionality

So the JSON result for fetching the branches is pretty complex. I tried a couple different ways of slicing and dicing it, but my bash-fu isn't strong enough. So instead I deferred to the usage of `python -mtool.json`. This should be included in any of the supported distributions, but I can certainly understand if you don't want a dependency on that being available. That said, it sure makes this a lot more painless, and now it works too, so there's that.

Anyways, I'm going to be using this, so figured I'd send this change your way.