Another try to fix testing workflow.

.github/workflows/tests.yml

@@ -18,23 +18,25 @@ jobs:
     strategy:
       matrix:
         os:
-          - ubuntu
+          - ubuntu-latest
         config:
-          #- [ ["2.7"], "py27"]
-          #- [ ["3.5"], "py35"]
-          #- [ ["3.6"], "py36"]
-          #- [ ["3.7"], "py37"]
-          #- [ ["3.8"], "py38"]
-          - [ ["2.7", "3.9"], "lint,clean,py27,py39,report"]
-          #- [ ["pypy-2.7"], "pypy"]
-          #- [ ["pypy-3.7"], "pypy3"]
-    runs-on: ubuntu-latest
+          #- [ "2.7", "py27"]
+          #- [ "3.5", "py35"]
+          #- [ "3.6", "py36"]
+          #- [ "3.7", "py37"]
+          #- [ "3.8", "py38"]
+          - [ "3.9", "lint,clean,py27,py39,report"]
+          #- [ "pypy-2.7", "pypy"]
+          #- [ "pypy-3.7", "pypy3"]
+    runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v4
       - name: Set up Python ${{ matrix.config[0] }}
         uses: actions/setup-python@v5
         with:
-          python-version:  ${{ matrix.config[0] }}
+          python-version: |
+              "2.7"
+              ${{ matrix.config[0] }}
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip