install 3.9 as 20.04 comes with eol 3.8

Author: assignUser

.github/workflows/python-wheels.yaml

@@ -53,6 +53,9 @@ jobs:
         fetch-tags: true
 
     - uses: actions/setup-python@v5
+      with:
+        python-version: '3.9'
+
     - name: Check that cmake is installed
       run: |
         cmake --version