Fix distribution upload breakage.

The upload phase now fails if there is anything unexpected in the long
description such as uninterpreted roles (e.g., `:class:`).  The ReST
specifications does call out that:

> Only pre-determined roles are recognized; unknown roles will
> generate errors.

I added a distcheck job in the tox.ini to make this easier to catch in
the future.

README.rst

@@ -50,13 +50,13 @@ the payload.
 
 If you are a `python-statsd`_ user, then the method names should look very familiar.  That is quite intentional.
 I like the interface and many others do as well.  There is one very very important difference though -- the
-``timing`` method takes the duration as the number of **seconds** as a :class:`float` instead of the number of
+``timing`` method takes the duration as the number of **seconds** as a ``float`` instead of the number of
 milliseconds.
 
 .. warning::
 
    If you are accustomed to using `python-statsd`_, be aware that the ``timing`` method expects the number of
-   seconds as a :class:`float` instead of the number of milliseconds.
+   seconds as a ``float`` instead of the number of milliseconds.
 
 .. _python-statsd: https://statsd.readthedocs.io/en/latest/
 

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = lint,py37,py38,py39,tornado5
+envlist = lint,distcheck,py37,py38,py39,tornado5
 toxworkdir = ./build/tox
 
 [testenv]
@@ -13,6 +13,17 @@ commands =
 	flake8 sprockets_statsd tests
 	yapf -dr sprockets_statsd tests
 
+[testenv:distcheck]
+deps =
+	twine
+	wheel
+commands =
+	rm -fr {envtmpdir}/dist
+	python setup.py sdist --dist-dir {envtmpdir}/dist
+	python setup.py bdist_wheel --dist-dir {envtmpdir}/dist
+	twine check {envtmpdir}/dist/*
+	rm -fr {envtmpdir}/dist
+
 [testenv:tornado5]
 deps =
 	tornado>=5,<6