chore(ci): run the tests on python 3.12 to 3.15

.github/workflows/ci.yaml

@@ -9,13 +9,18 @@ on:
 jobs:
   test:
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        # Oldest supported version from the readme up to the newest one
+        python-version: ["3.12", "3.13", "3.14", "3.15"]
     steps:
       - uses: actions/checkout@v7
 
-      - name: Set up Python
+      - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v7
         with:
-          python-version: "3.15"
+          python-version: ${{ matrix.python-version }}
 
       - name: Install dependencies
         run: pip install -r requirements-dev.txt

test/ui_test_support.py

@@ -5,7 +5,6 @@
 instead of being skipped, e.g. in CI where they must always run.
 """
 
-import importlib.util
 import os
 import unittest
 from typing import Callable, TypeVar
@@ -18,8 +17,15 @@
 def has_tkinter() -> bool:
     """
     Returns if tkinter can be imported.
+    The module can exist while the Tk library of the system is missing,
+    so it is really imported instead of only searched.
     """
-    return importlib.util.find_spec("tkinter") is not None
+    try:
+        # pylint: disable=import-outside-toplevel,unused-import
+        import tkinter  # noqa: F401
+    except ImportError:
+        return False
+    return True
 
 
 def has_display() -> bool: