unittest using python3

Author: brentru

.travis.yml

@@ -12,7 +12,7 @@ install:
 script:
 - cd docs && sphinx-build -E -W -b html . _build/html && cd ..
 - cd tests/
-- python -m unittest discover
+- python3 -m unittest discover
 deploy:
 - provider: releases
   api_key: "$GITHUB_TOKEN"