Test diagnostics

Author: ndevenish

.github/workflows/build_wheels.yml

@@ -56,7 +56,7 @@ jobs:
               env:
                   CIBW_SKIP: cp2* cp35* pp*
                   CIBW_TEST_COMMAND: pytest --regression {package}/tests
-                  CIBW_BEFORE_TEST: pip install pytest dials-data
+                  CIBW_BEFORE_TEST: pip install pytest dials-data; python3 -c "import pycbf, pathlib; print(pycbf.__file__ + '\n'); print(list(pathlib.Path(pycbf.__file__).parent.iterdir()))"
                   CIBW_BUILD_FRONTEND: 'pip; args: -vvv'
 
             - uses: actions/upload-artifact@v4