I haven't solved the issue yet, but if I do, I'll push up a review.

I had some time to track down the error

AttributeError: 'method' object has no attribute '__yaql_function__'

which turned out to be a Python 3 issue and I've got a review up here for it https://review.opendev.org/#/c/760470/

I've fixed a couple of Python 3 specific issues recently, so I'd recommend you either use the Train version with Python 2 or if you want to run on Python 3 then you'll need to use master right now with my patches on top.

cheers,
Andy