RTD build fails with module not found `sphinxcontrib.cadquery`

[sethfischer]

Read the Docs build fails with ModuleNotFoundError: No module named 'sphinxcontrib.cadquery':

python -m sphinx -T -E -b html -d _build/doctrees -D language=en . $READTHEDOCS_OUTPUT/html
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Configuration error:
There is a programmable error in your configuration file:

Traceback (most recent call last):
  File "/home/docs/checkouts/readthedocs.org/user_builds/sphinxcontrib-cadquery/envs/39/lib/python3.9/site-packages/sphinx/config.py", line 350, in eval_config_file
    exec(code, namespace)
  File "/home/docs/checkouts/readthedocs.org/user_builds/sphinxcontrib-cadquery/checkouts/39/docs/conf.py", line 7, in <module>
    import sphinxcontrib.cadquery
ModuleNotFoundError: No module named 'sphinxcontrib.cadquery'

When added to .readthedocs.yaml: build.jobs.post-install the following also fails:

python -c "import sphinxcontrib.cadquery; print(sphinxcontrib.cadquery.__version__)"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ModuleNotFoundError: No module named 'sphinxcontrib.cadquery'

Last successful build: Build #19376393 dated Feb. 4, 2023. 1:54 a.m. First failed build: Build #19562383 dated Feb. 22, 2023. 9:39 a.m.

The poetry install command reports successful installation of the project package:

poetry install
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Installing the current project: sphinxcontrib-cadquery (0.4.0)

Dependencies installed with poetry install are available for import e.g cadquery, just not the current (root) project.

[sethfischer]

readthedocs/readthedocs.org#10058