Expose Poetry's virtualenv

If the user doesn’t have an active virtualenv, Poetry is already creating and using a default per-project virtualenv behind the scenes. There is no easy way to get to it after it’s created.

If you’d be willing to accept a PR to this effect, I’d be happy to contribute the following:

• add a poetry shell command equivalent to pipenv shell
• make poetry add/remove/install output the path to the virtualenv that it’s using if there is no active virtualenv

I know that your current available alternative is poetry run. My problem with it is that it gets verbose fast. poetry run python -m X instead of just X in an activated virtualenv.

[ambv]

I don’t use Windows so I’ll leave that part as an exercise to the reader.

[jaroel]

Here’s a workaround to get it: $ poetry run which python /Users/roel/Library/Caches/pypoetry/virtualenvs/koei-py3.6/bin/python