Fix testing workflow.

Fix chain of `tox` envs to run (include also Python 2.7) and upgrade
action versions used in workflow.

.github/workflows/tests.yml

@@ -25,14 +25,14 @@ jobs:
           #- ["3.6", "py36"]
           #- ["3.7", "py37"]
           #- ["3.8", "py38"]
-          - ["3.9", "lint,py39,report"]
+          - ["3.9", "lint,clean,py27,py39,report"]
           #- ["pypy-2.7", "pypy"]
           #- ["pypy-3.7", "pypy3"]
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Set up Python ${{ matrix.config[0] }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v3
         with:
           python-version:  ${{ matrix.config[0] }}
       - name: Install dependencies