Fail loudly instead of skipping cea_module fixture on broken CI builds

[djkees]

Summary

The session-scoped cea_module pytest fixture in source/bind/python/tests/conftest.py, which nearly every Python test depends on, called pytest.skip(...) when import cea or cea.is_initialized() failed. A broken build (compile failure, missing extension, botched CMake step) made every dependent test report "skipped" rather than "failed," and pytest exits 0 on an all-skipped run — so basic_build.yml's python-tests job could show green even though nothing actually ran.

djkees#89

Changes

• conftest.py: the fixture now checks the CI/GITHUB_ACTIONS environment variables (set automatically by GitHub Actions runners). When set, an import or init failure calls pytest.fail(...) instead of pytest.skip(...), so the run errors out with a nonzero exit code. Outside CI (e.g. local dev without a built extension), the original skip behavior is unchanged.

Testing

• pytest source/bind/python/tests -q (real dev environment, extension built): 116 passed, confirming no regression.
• Manual before/after check with a throwaway test that poisons sys.modules["cea"] to force an import failure: without CI set, 1 skipped (unchanged); with CI=true, 1 error / Failed: cea import failed: ... (new behavior).

Compatibility / Numerical behavior

• No expected changes to numerical results

Test-infrastructure only; no solver/binding logic touched.

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Drafted with Claude's assistance

• Verified by reading the original conftest.py and reproducing both the old (skip) and new (fail) behavior directly, in both a clean sandbox and a real dev environment, before and after the change.
• Full existing Python test suite (116 tests) re-run and confirmed passing after the change.