try just python for report,codecov

Author: altendky

tox.ini

@@ -15,7 +15,8 @@ basepython =
     py36: {env:TOXPYTHON:python3.6}
     py37: {env:TOXPYTHON:python3.7}
     py38: {env:TOXPYTHON:python3.8}
-    {bootstrap,clean,check,report,codecov}: {env:TOXPYTHON:python3}
+    {bootstrap,clean,check}: {env:TOXPYTHON:python3}
+    {report,codecov}: {env:TOXPYTHON:python}
 setenv =
     PYTHONPATH={toxinidir}/tests
     PYTHONUNBUFFERED=yes