Update setuptools to 40.9.0

[pyup-bot]

This PR updates setuptools from 40.8.0 to 40.9.0.

Changelog

40.9.0

-------

* 1675: Added support for ``setup.cfg``-only projects when using the ``setuptools.build_meta`` backend. Projects that have enabled PEP 517 no longer need to have a ``setup.py`` and can use the purely declarative ``setup.cfg`` configuration file instead.
* 1720: Added support for ``pkg_resources.parse_requirements``-style requirements in ``setup_requires`` when ``setup.py`` is invoked from the ``setuptools.build_meta`` build backend.
* 1664: Added the path to the ``PKG-INFO`` or ``METADATA`` file in the exception
text when the ``Version:`` header can't be found.
* 1705: Removed some placeholder documentation sections referring to deprecated features.

Links

• PyPI: https://pypi.org/project/setuptools
• Changelog: https://pyup.io/changelogs/setuptools/
• Repo: https://github.com/pypa/setuptools