Just to try this crazy idea to have tox install Cython for testenv:pypy.

[dHannasch]

Resolves #161. Maybe.

Okay, this is...weird.

ERROR: invocation failed (exit code 1), logfile: /home/travis/build/ionelmc/cookiecutter-pylibrary/python-nameless/.tox/pypy/log/pypy-2.log
================================== log start ===================================
Looking in links: file:///home/travis/.pip/wheels
Processing ./.tox/.tmp/package/1/nameless-1.0.0.zip
  Could not find a version that satisfies the requirement cython (from versions: )

But setup_requires didn't ask for cython. It asked for Cython. The requirement cython must be coming from somewhere else.

We could probably from _setuputils import PYPY in setup.py, but really the requirement is coming from pyproject.toml.
https://gemfury.com/squarecapadmin/python:gevent/-/content/setup.py

Strangely, even with "cffi>=1.0.0; platform_python_implementation != 'PyPy'", it still tries to install cffi>=1.0.0 and still complains of not finding it.