ubuntu-latest is moving to 22, which doesnt support 2.7 - see actions/runner-images#6399

Author: wimglenn

.github/workflows/tests.yml

@@ -15,7 +15,7 @@ jobs:
     strategy:
       matrix:
         os:
-        - ubuntu-latest
+        - ubuntu-20.04
         - macos-latest
         - windows-latest
         python-version: