Drop support for near-end-of-life Python 3.9

Author: hartwork

.github/workflows/test.yml

@@ -14,7 +14,7 @@ jobs:
   run_test_suite:
     strategy:
       matrix:
-        python-version: [3.9, 3.13]  # no current need for in-between versions
+        python-version: ["3.10", 3.13]  # no current need for in-between versions
     name: Run the Test Suite
     runs-on: ubuntu-24.04
     steps:

setup.py

@@ -20,14 +20,13 @@
         "Operating System :: OS Independent",
         "Topic :: Software Development",
         "Programming Language :: Python :: 3",
-        "Programming Language :: Python :: 3.9",
         "Programming Language :: Python :: 3.10",
         "Programming Language :: Python :: 3.11",
         "Programming Language :: Python :: 3.12",
         "Programming Language :: Python :: 3.13",
         "Programming Language :: Python :: 3 :: Only",
     ],
-    python_requires='>=3.9',
+    python_requires='>=3.10',
     setup_requires=[
         'setuptools>=38.6.0',  # for long_description_content_type
     ],