Pin against sphinx 1.8.0 due to sphinx-doc/sphinx#5417.

build_meta.get_requires_for_build_sdist does not include wheel

Suppress warnings in importer.find_module.

Remove compatibility shim for bytes type

link to setuptools doc

The type bytes is available on all supported Pythons. Makes the code
more forward compatible with Python 3.

the wheel package is not required to build a source distribution

Resolves #1474.

Fix for Unicode handling in PEP 518 backend

setuptools: fix regression with `egg_info` command

Ensure version is tagged only once.

Prepare 40.1.0

Add an empty .gitignore to changelog.d to prevent the directory from
being deleted when it is emptied out during a release.