Add support for Python 3.10

Author: nicoddemus

.github/workflows/main.yml

@@ -55,7 +55,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python: ["3.6", "3.7", "3.8", "3.9"]
+        python: ["3.6", "3.7", "3.8", "3.9", "3.10"]
         include:
           - python: "3.6"
             tox_env: "py36-pytestlatest"
@@ -65,6 +65,8 @@ jobs:
             tox_env: "py38-pytestlatest"
           - python: "3.9"
             tox_env: "py39-pytestlatest py39-pytest53"
+          - python: "3.10"
+            tox_env: "py310-pytestlatest"
 
     steps:
     - uses: actions/checkout@v1
@@ -98,7 +100,7 @@ jobs:
     - name: Set up Python
       uses: actions/setup-python@v1
       with:
-        python-version: "3.7"
+        python-version: "3.9"
     - name: Install wheel
       run: |
         python -m pip install --upgrade pip