test_compilefuncs_and_path_sanity: 'yield' keyword is allowed in fixtures, but not in tests

Recent enough pytest fails to collect `test_compilefuncs_and_path_sanity` with this error:
```
_________________ ERROR collecting testing/code/test_source.py _________________
'yield' keyword is allowed in fixtures, but not in tests (test_compilefuncs_and_path_sanity)
```