[QUESTION] Check validity of `setup.py` in build

[dhermes]

H/T to http://inre.dundeemt.com/2014-05-17/pypi-setup-py-keeping-a-dry-long_description/ (I was Googling around for DRY in setup.py)

python setup.py check --restructuredtext --strict

---

For example, running it on the post #2442 version gives:

$ python setup.py check --restructuredtext --strict
running check
warning: check: Duplicate implicit target name: "contributing".

warning: check: Duplicate implicit target name: "license".

error: Please correct your package.

because we have sections named license and contributing as well as links with those names. This could be fixed via

diff --git a/README.rst b/README.rst
index 715368b..bbf0f72 100644
--- a/README.rst
+++ b/README.rst
@@ -96,16 +96,16 @@ Contributing

 Contributions to this library are always welcome and highly encouraged.

-See `CONTRIBUTING`_ for more information on how to get started.
+`See CONTRIBUTING`_ for more information on how to get started.

-.. _CONTRIBUTING: https://github.com/GoogleCloudPlatform/google-cloud-python/blob/master/CONTRIBUTING.rst
+.. _See CONTRIBUTING: https://github.com/GoogleCloudPlatform/google-cloud-python/blob/master/CONTRIBUTING.rst

 License
 -------

-Apache 2.0 - See `LICENSE`_ for more information.
+Apache 2.0 - `See LICENSE`_ for more information.

-.. _LICENSE: https://github.com/GoogleCloudPlatform/google-cloud-python/blob/master/LICENSE
+.. _See LICENSE: https://github.com/GoogleCloudPlatform/google-cloud-python/blob/master/LICENSE

 .. |build| image:: https://travis-ci.org/GoogleCloudPlatform/google-cloud-python.svg?branch=master
    :target: https://travis-ci.org/GoogleCloudPlatform/google-cloud-python

[theacodes]

We should do this. Google-auth does it.

[dhermes]

@jonparrott Jinx! I'm going to send a PR for adding this to nox -e lint for the subpackages. Should I add a nox -e lint for the top-level package?

[lukesneeringer]

I would prefer it be a separate nox session if possible.