feat: support Python 3.10

Adds official support for Python 3.10 by including this version in the
test suite.

.github/workflows/ci.yml

@@ -27,7 +27,7 @@ jobs:
       - name: Set up Python 3.8
         uses: actions/setup-python@v2
         with:
-          python-version: 3.8
+          python-version: "3.10"
       - name: Install tox
         run: |
           python -m pip install --upgrade pip
@@ -52,7 +52,7 @@ jobs:
     strategy:
       max-parallel: 4
       matrix:
-        python-version: [3.7, 3.8, 3.9]
+        python-version: ["3.7", "3.8", "3.9", "3.10"]
 
     steps:
       - name: Clone repo

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = coverage-clean,test-py{37,38,39}, check, coverage
+envlist = coverage-clean,test-py{37,38,39,310}, check, coverage
 
 [testenv]
 extras = test
@@ -18,7 +18,7 @@ commands = coverage erase
 depends =
 
 [testenv:coverage]
-depends = test-py{37,38}
+depends = test-py{37,38,39,310}
 deps =
     coverage
 skip_install = true
@@ -41,3 +41,4 @@ python =
     3.7: py37, coverage
     3.8: py38, coverage
     3.9: py39, coverage
+    3.10: py310, coverage