Use tox in CI.

Author: JulienPalard

.github/workflows/tests.yml

@@ -25,12 +25,12 @@ jobs:
           cache-dependency-path: .github/workflows/tests.yml
       - name: Upgrade pip
         run: python -m pip install --upgrade pip
-      - name: Install pytest
-        run: python -m pip install --upgrade pytest
+      - name: Install tox
+        run: python -m pip install --upgrade tox
       - name: Install sphinx-lint to pull dependencies
         run: python -m pip install -v .
       - name: Download more tests from friend projects
         if: matrix.python-version == '3.11' && matrix.os == 'ubuntu-latest'
         run: sh download-more-tests.sh
       - name: run tests
-        run: python -m pytest
+        run: tox