https://sphinx-doc.org is unreachable, but is linked from the PyPI page:
https://pypi.org/project/Sphinx/. Switch to https://www.sphinx-doc.org/
instead.

.. note::

   $ find sphinx tests LICENSE doc/conf.py -type f -exec sed -i '' -e 's/2007\-20../2007-2021/' {} \;
   $ git co sphinx/locale/**/*.js sphinx/templates/epub3/mimetype

Keep imports alphabetically sorted and their order homogeneous across
Python source files.

The isort project has more feature and is more active than the
flake8-import-order plugin.

Most issues caught were simply import ordering from the same module.
Where imports were purposefully placed out of order, tag with
isort:skip.

`bdb.BdbQuit` is used when quitting the debugger.
It should not a) cause the debugger to be started (with `-P` / `--pdb`),
and b) not a "crash" to be logged.

This helps when using `pdb.set_trace()` manually, and quitting it with
`q`.

It gets used in `build_main`, and `BuildDoc.run` (distutils command).