MyST builds report success when code execution fails

[brian-rose]

I think this is a bug in the most recent mystmd-based build-book workflow.

Our nightly builds and CI tests are reporting success when we run

myst build --execute --html

even if there is a failure in the code execution.

An example is here:
https://projectpythia.org/radiative-feedback-cookbook/_preview/29/notebooks/feedback-analysis/manual-calc

It's possible that adding --ci to the myst build command will restore the desired behavior.

[brian-rose]

MyST doesn't seem to have this capability currently. Issue open:
jupyter-book/mystmd#2113

[brian-rose]

For now, this represents a significant regression in our quality control, because our CI tests do not flag code failures in notebooks.