`poetry use pypy3` switches to a Python 3.6 venv if it already exists

• I am on the latest Poetry version.
• I have searched the issues of this repo and believe that this is not a duplicate.
• If an exception occurs when executing a command, I executed it again in debug mode (-vvv option).

• OS version and name: Ubuntu 18.04
• Poetry version: 1.0.3
• Link of a Gist with the contents of your pyproject.toml file: https://gist.github.com/thedrow/5b7d581db41f2d8d40ca9e4c9c98d283

Issue

When I try to switch my environment to PyPy3 using poetry use pypy3 but have previously typed poetry use 3.6 poetry switches to the CPython 3.6 virtualenv instead of creating a new virtualenv for pypy3. You can reproduce this by doing the following:

$ poetry env use 3.6
Using virtualenv: /home/thedrow/.cache/pypoetry/virtualenvs/jumpstarter-H8PwDp0q-py3.6
$ poetry env use pypy3
Using virtualenv: /home/thedrow/.cache/pypoetry/virtualenvs/jumpstarter-H8PwDp0q-py3.6
$ poetry run which pypy3
/home/thedrow/.pyenv/shims/pypy3 # should be the virtualenv's pypy

[thedrow]

Just include the platform if it’s not CPython in the virtualenv’s name.

[PetterS]

With some more time that PR now seems to work, at least with my installation of pypy.