make PythonPackage easyblock compatible with --sanity-check-only by loading module early during sanity check step

[boegel]

requires:

• add sanity_check_load_module method to EasyBlock to provide control over when module is loaded during sanity check step easybuild-framework#4125

fixes #2745

[boegel]

Test report by @boegel

Overview of tested easyconfigs (in order)

• SUCCESS Python-3.9.6-GCCcore-11.2.0.eb
• FAIL (build issue) xarray-0.15.1-foss-2019b-Python-3.7.4.eb (partial log available at https://gist.github.com/8051af7ae32f0a1ef3a87538ff5e210d)
• FAIL (build issue) scikit-learn-0.24.2-intel-2021a.eb (partial log available at https://gist.github.com/7a3a908235cf52801a0f3999d80f370e)
• SUCCESS matplotlib-3.5.2-foss-2022a.eb
• FAIL (build issue) h5py-3.6.0-intel-2021b.eb (partial log available at https://gist.github.com/83d92ab96ecdd5492833d74c696ac379)

Build succeeded for 2 out of 5 (5 easyconfigs in total)
node3139.skitty.os - Linux RHEL 8.4, x86_64, Intel(R) Xeon(R) Gold 6140 CPU @ 2.30GHz (skylake_avx512), Python 3.6.8
See https://gist.github.com/8a8fb30fb0352c57ebca18d86bb9ffd2 for a full test report.

[boegel]

Hmm, clearly not working yet as intended...

[boegel]

A fix in extensioneasyblock.py was also needed (see easybuilders/easybuild-framework@e282dbe), as well as not generating/loading the fake module prior to running pip check in PythonPackage.sanity_check_step (see 57288b6).

[boegel]

Test report by @boegel

Overview of tested easyconfigs (in order)

• SUCCESS Python-3.9.6-GCCcore-11.2.0.eb
• SUCCESS xarray-0.15.1-foss-2019b-Python-3.7.4.eb
• SUCCESS scikit-learn-0.24.2-intel-2021a.eb
• SUCCESS matplotlib-3.5.2-foss-2022a.eb
• SUCCESS h5py-3.6.0-intel-2021b.eb

Build succeeded for 5 out of 5 (5 easyconfigs in total)
node3102.skitty.os - Linux RHEL 8.4, x86_64, Intel(R) Xeon(R) Gold 6140 CPU @ 2.30GHz (skylake_avx512), Python 3.6.8
See https://gist.github.com/2c71f107ee6f26b04160539cc417b1ea for a full test report.

[akesandgren]

LGTM

[akesandgren]

Going in, thanks @boegel!