Xeus python build addon

[martinRenou]

JupyterLite command line addon.

This adds a --XeusPythonEnv.packages CLI option to jupyter lite build allowing to install Python package in the xeus-python-lite deployment:

jupyter lite build --XeusPythonEnv.packages=numpy,matplotlib,ipywidgets

The important changes from the PR are the following:

• Build xeus-python-kernel under the path /tmp/xeus-python-kernel in the DockerFile
• Add a new entry point for jupyterlite in the Python package
  • This new entry point adds the XeusPythonEnv jupyterlite addon which allows to create a custom emscripten-32 conda env that will be used for the xeus-python deployment
  • This env is created under the same path as the docker build /tmp/xeus-python-kernel
  • Once the env is created and packed with emboa, we move the resulting python_data.data and python_data.js at the right place for the labextension to fetch.

TODO:

• Add multiple CI jobs for testing with mamba's Python API, mamba CLI, micromamba CLI and conda CLI
• Add an emboa dependency (we need to publish emboa on Pypi and conda-forge)
• Add support for conda CLI
• Make sure this addon runs after the core Federated extension addon (question asked in Make a addon that runs after FederatedExtensionsAddon jupyterlite#647)
• Try to remove some @ts-ignore calls

[jtpio]

Really cool!

This adds a --XeusPythonEnv.packages CLI option to jupyter lite build allowing to install Python package in the xeus-python-lite deployment:

Note for later: it will also be possible to configure this with a XeusPythonEnv key in a jupyter_lite_config.json file.

[jtpio]

Nice.

Wondering how this would interact with the existing --ignore-sys-prefix lite flag? (to not pick up extensions from the build environment)

Maybe it's fine in that case, since the prebuilt lab extensions come from a separate (emscripten) env.

[martinRenou]

I guess a sensible approach for the xeus-python addon would be to ignore that flag? (I'll check if it is ignored)

A typical user would probably always want to have the labextensions from the emscripten env be included? Otherwise they would not have installed them.

[martinRenou]

Note for later: it will also be possible to configure this with a XeusPythonEnv key in a jupyter_lite_config.json file.

Indeed! I should add some documentation for this.