Notebooks built with `--execute` can fail (maybe due to session path issues)

[stevejpurves]

Description

When we run myst start with the execute flag, if we have a notebook in a subfolder that relies on a relative path, the execution od the notebook can fail / produce an error. This can be because the path for the notebook session is not correctly set on execution.

As the same notebook would execute correctly inside of JupyterLab without modification, then we have the expectation that it should also execute correctly when running with via myst build or myst start with the --execute flag.

Proposed solution

In live compute mode, the Jupyter package automatically looks for leading path segments to the current notebook and then uses those to set the kernel path appropriately see here, and without that intervention, we would be experiencing the same error in Live Compute, (and have done in the past).

Potentially the solution here is similar?

Additional notes

It's easily reproduced using the https://github.com/jupyter-book/example-outputs site, where the multiple and multiple-nb pages show the problem.

[agoose77]

@stevejpurves can you share how you're seeing this? Locally and on CI, this page is fine: https://jupyter-book.github.io/example-outputs/multiple-nb/

I explicitly recall setting the kernel path because this was a previous bug.