Setup scripts can use pytest-runner to add setup.py test support
for pytest runner.

Notice: pytest-runner depends on deprecated features of setuptools and relies on
features that break security mechanisms in pip.

It is recommended that you:

- Remove 'pytest-runner' from your setup_requires, preferably removing the
  setup_requires option.
- Remove 'pytest' and any other testing requirements from tests_require,
  preferably removing the tests_requires option.
- Select a tool to bootstrap and then run tests such as tox.

WWW: https://github.com/pytest-dev/pytest-runner
