Add Support for Python 3.9

Author: LKaemmerling

.github/workflows/tests-unit.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.5, 3.6, 3.7, 3.8]
+        python-version: [3.5, 3.6, 3.7, 3.8, 3.9]
     steps:
     - name: Checkout repo
       uses: actions/checkout@v2

CONTRIBUTING.rst

@@ -30,7 +30,7 @@ features (it's not a must though).
 
 Python version and libraries
 ============================
-* Python 3.5, 3.6, 3.7, 3.8:
+* Python 3.5, 3.6, 3.7, 3.8, 3.9:
 
   Ryu supports multiple Python versions.  CI tests on GitHub Actions is running
   on these versions.

setup.cfg

@@ -17,6 +17,8 @@ classifier =
     Programming Language :: Python :: 3.5
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
+    Programming Language :: Python :: 3.8
+    Programming Language :: Python :: 3.9
     Operating System :: Unix
 keywords =
     openflow

tox.ini

@@ -1,12 +1,13 @@
 [tox]
-envlist = py35,py36,py37,py38,pypy,pycodestyle,autopep8
+envlist = py35,py36,py37,py38,py39,pypy,pycodestyle,autopep8
 
 [gh-actions]
 python =
   3.5: py35
   3.6: py36, pycodestyle, autopep8
   3.7: py37
   3.8: py38
+  3.9: py39
 
 [testenv]
 deps =