pytest-asyncio incompatibility

[tony]

• Not compatible with --doctest-modules --doctest-ignore-import-errors pytest-dev/pytest-asyncio#797
• https://github.com/search?q=repo%3Apytest-dev%2Fpytest%20doctest-ignore-import-errors&type=code
• asyncio: Asynchronous libtmux tmux-python/libtmux#554