ci: add py3.9 to gh-actions test matrix

Author: edaniszewski

.github/workflows/test.yaml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        py-version: ['3.8']
+        py-version: ['3.8', '3.9']
     name: Python ${{ matrix.py-version }} Test
     steps:
     - name: Checkout

tox.ini

@@ -1,19 +1,21 @@
 [tox]
-envlist = py{36,37,38}
+envlist = py{36,37,38,39}
 skip_missing_interpreters=True
 
 [gh-actions]
 python =
     3.6: py36
     3.7: py37
     3.8: py38,lint
+    3.9: py39
 
 [testenv]
 basepython =
     py35: python3.5
     py36: python3.6
     py37: python3.7
     py38: python3.8
+    py39: python3.9
 deps =
     pytest
     pytest-cov