add twine check in tox

Author: Dan Choi

tox.ini

@@ -72,3 +72,14 @@ deps =
     pylint==2.1.1
 commands =
     python -m pylint --rcfile=.pylintrc -j 0 src/sagemaker
+
+[testenv:twine]
+basepython = python
+# twine check was added starting in 1.12.0
+# https://github.com/pypa/twine/blob/master/docs/changelog.rst
+deps =
+    twine>=1.12.0
+# https://packaging.python.org/guides/making-a-pypi-friendly-readme/#validating-restructuredtext-markup
+commands =
+    python setup.py sdist
+    twine check dist/*.tar.gz