when having tox.ini use Python from one of the environments for auto complete

Hello, 

So here's my problem PyCharm has a decent tox support, however it still relies on an outside environment for syntax check and everything else; so when I open a new project I need to manually install project dependencies into the project interpreter. Here's how I think this could be helped:

Allow to automatically or easily select one of the tox environments as the project interpreter (e.g. right click on tox.ini -> set project interpreter -> list of existing envs.

Or because the Python interpreter needs tox (which is not a project dependency), in case a pycharm env is defined, automatically pick and use that one. 

What do you think?