The issue arose if logging was initialized while capturing was enabled and then capturing streams were closed before process exit, leading to the logging module to complain.
Use 'tryfirst' for capturing hooks so they can start capturing as early as possible, including when conftests add output in runtest_setup hooks.
- pytest.py is new module, making "python -m pytest" work always - _pytest/*.py now contains core.py, hookspec and the plugins, no sub packages