Took into account the DeprecationWarning by Travis CI

.travis.yml

@@ -19,4 +19,4 @@ python:
     - 3.8
     - 3.7
     - 3.6
-script: python setup.py test
+script: tox

tox.ini

@@ -19,7 +19,7 @@ ignore=E501,F401,F841,W504
 setenv =
     PYTHONPATH = {toxinidir}
 deps =
-commands = python -m unittest discover
+commands = python setup.py test
 
 ; If you want to make tox run the tests with the same versions, create a
 ; requirements.txt with the pinned versions and uncomment the following lines: