The reproduction here is a bit complicated because I haven't quite narrowed it down yet but here goes.
I noticed this initially when my build was running indefinitely (and eventually failing) here : https://ci.appveyor.com/project/asottile/pre-commit/branch/master/job/r57jhonel6dlgd9d
My "minimal" reproduction is as follows:
- git clone git://github.com/pre-commit/pre-commit
- cd pre-commit
- virtualenv venv
- . venv/Scripts/activate
- pip install -r requirements-dev.txt
- pip install 'coverage<4'
- coverage run -m pytest tests -k test_parse_merge # Runs and succeeds
- pip install 'coverage>=4'
- coverage run -m pytest tests -k test_parse_merge # Hangs forever
I've attached a screenshot (the contrast sucks because the window froze on my VM)