Add Python 3.9 to the testing matrix

Author: simenheg

.github/workflows/continous-integration.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python: [3.6, 3.7, 3.8]
+        python: [3.6, 3.7, 3.8, 3.9]
 
     steps:
     - uses: actions/checkout@v2

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py36,py37,py38,flake8,black,mypy
+envlist = py36,py37,py38,py39,flake8,black,mypy
 
 [testenv]
 deps=