Remove _scripts, use new PyPI module instead

[matthew-brett]

I've refactored the notebook post-processing into the jljb module.

[jarrodmillman]

Sorry, I missed something. Are we still testing on multiple versions of Python?

[matthew-brett]

You mean - why did I delete test.yml? Jupyter Book doesn't support the doctesting that a bare Sphinx build does. In a way, that's a boon, because there was some confusing markup that the user sees, in order to satisfy doctest. But in any case, we can't test in the same way.

I did put in some test machinery though, that you can see described in CONTRIBUTING.md - in the form of cells marked remove-cell with asserts in them. These don't appear in the built output or the JupyterLite notebooks, but do get run as part of the book build process.

[matthew-brett]

@jarrodmillman - I wasn't sure what you were asking for, but I restored the test.yml file - although it only runs one test:

pytest .
==================================================== test session starts ====================================================
platform darwin -- Python 3.12.2, pytest-8.4.2, pluggy-1.6.0
rootdir: /Volumes/zorg/mb312/dev_trees/scientific-python-lectures
configfile: pyproject.toml
plugins: anyio-4.8.0
collected 1 item                                                                                                            

intro/language/solutions/test_dir_sort.py .                                                                           [100%]

===================================================== 1 passed in 1.45s =====================================================

Otherwise, this is a straight refactor of the support code out into its own module, so I can only see a win here, compared to status quo.

[matthew-brett]

Another plea for this one.

Also see :#864