Run tests with packaging 24.0 in CI

Author: dnicolodi

.github/workflows/main.yml

@@ -48,6 +48,13 @@ jobs:
           - ubuntu-latest
           - macos-latest
           - windows-latest
+        tox-environment:
+          - py
+        include:
+          # Test with the oldest supported ``packaging`` version.
+          - platform: ubuntu-latest
+            python-version: "3.8"
+            tox-environment: py-packaging240
     runs-on: ${{ matrix.platform }}
     steps:
       - uses: actions/checkout@v4.2.2
@@ -59,7 +66,7 @@ jobs:
       - name: Run type-checking
         run: python -m tox -e types
       - name: Run tests
-        run: python -m tox -e py
+        run: python -m tox -e ${{ matrix.tox-environment }}
 
   # Because the tests can be flaky, they shouldn't be required for merge, but
   # it's still helpful to run them on PRs. See: