use in image a 'green' python version

.github/workflows/ci_orig.yml

@@ -2,14 +2,17 @@ name: ci
 
 on: [push, pull_request]
 
+env:
+  pyver: 3.11
+
 jobs:
 
   tests:
     runs-on: ubuntu-latest
     timeout-minutes: 30
     strategy:
       matrix:
-        python-version: ['3.10','3.11','3.12']
+        python-version: ['3.9','3.10','3.11','3.12']
         aiida-version: ['stable']
 
     services:
@@ -55,10 +58,10 @@ jobs:
     timeout-minutes: 15
     steps:
     - uses: actions/checkout@v2
-    - name: Set up Python 3.10
+    - name: Set up Python $pyver
       uses: actions/setup-python@v2
       with:
-        python-version: "3.10"
+        python-version: "$pyver"
     - name: Install python dependencies
       run: |
         pip install --upgrade pip
@@ -71,10 +74,10 @@ jobs:
     timeout-minutes: 15
     steps:
     - uses: actions/checkout@v2
-    - name: Set up Python 3.10
+    - name: Set up Python $pyver
       uses: actions/setup-python@v2
       with:
-        python-version: "3.10"
+        python-version: "$pyver"
     - name: Install python dependencies
       run: |
         pip install --upgrade pip