make tox use expected python version

.github/workflows/tests.yml

@@ -54,5 +54,5 @@ jobs:
       - name: Install tox
         run: pip install tox
       - name: Run tests
-        run: tox -e ${{ matrix.python }}
+        run: tox -e py$(sed -e 's/\.//' <<< ${{ matrix.python }})
         timeout-minutes: 5

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = {3.6,3.7,3.8,3.9,3.10}
+envlist = py{36,37,38,39,310}
 
 [testenv]
 commands = make check