Enable tests on Python 3.9

Author: pganssle

.github/workflows/tests.yml

@@ -8,15 +8,15 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        python-version: [2.7, 3.6, 3.7, 3.8]
+        python-version: [2.7, 3.6, 3.7, 3.8, 3.9]
         os: ["ubuntu-latest", "windows-latest", "macos-latest"]
     env:
       TOXENV: py
 
     steps:
     - uses: actions/checkout@v2
     - name: ${{ matrix.python-version }} - ${{ matrix.os }}
-      uses: actions/setup-python@v1
+      uses: actions/setup-python@v2
       with:
         python-version: ${{ matrix.python-version }}
     - name: Install dependencies