Quote Python version 3.9 in GitHub Actions

adamchainz · adamchainz · commit b3a9f478ff2a · 2025-05-25T16:39:08.000+01:00
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
@@ -20,7 +20,7 @@ jobs:
     strategy:
       matrix:
         python-version:
-        - 3.9
+        - '3.9'
         - '3.10'
         - '3.11'
         - '3.12'
