Add a code coverage testenv to the tox config

Author: hackebrot

tox.ini

@@ -6,7 +6,13 @@ deps =
     pytest
     pytest-mock
     responses
-commands = pytest {posargs:tests} -v
+commands = pytest -v {posargs:tests}
+
+[testenv:cov]
+deps =
+    {[testenv]deps}
+    pytest-cov
+commands = pytest -v --cov labels {posargs:tests}
 
 [testenv:flake8]
 deps = flake8