Merge pull request kragniz#1562 from kragniz/ci-python39

python38 -> python39 in CI

Author: kragniz

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py38, flake8
+envlist = py39, flake8
 skipsdist=True
 
 [testenv:flake8]
@@ -45,6 +45,3 @@ application-import-names = etcd3
 max-complexity = 10
 # TODO add docstrings for public methods, modules, etc
 ignore = D1, W503
-
-[travis]
-python = 3.6: py36, flake8