Jupytext does not exist for automated tests

[sklbancor]

This is the run_tests.py that runs the tests

That's how it looks like when it runs on Github (suggesting JupyText is not available)

In other words -- unless someone does run_tests on the local machine first, NBTests will not be converted into .py tests AND THEREFORE THOSE TESTS WILL NOT RUN ON THE SERVER, EVEN THOUGH IT LOOKS LIKE THEY DO.

This is obviously dangerous and should be rectified.