Drop Python 3.9 support (#237)

* Initial plan

* Drop Python 3.9 support, set minimum to Python 3.10

Co-authored-by: seanthegeek <44679+seanthegeek@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: seanthegeek <44679+seanthegeek@users.noreply.github.com>

Author: Copilot

.github/workflows/python-tests.yaml

@@ -16,10 +16,10 @@ jobs:
 
     steps:
     - uses: actions/checkout@v4
-    - name: Set up Python 3.9
+    - name: Set up Python 3.10
       uses: actions/setup-python@v4
       with:
-        python-version: "3.9"
+        python-version: "3.10"
     - name: Install Python dependencies
       run: |
         python -m pip install --upgrade pip

docs/source/installation.md

@@ -1,6 +1,6 @@
 # Installation
 
-`checkdmarc` requires Python 3.
+`checkdmarc` requires Python 3.10 or later.
 
 On Debian or Ubuntu systems, run:
 

pyproject.toml

@@ -9,7 +9,7 @@ name = "checkdmarc"
 dynamic = [
     "version",
 ]
-python_requires = ">=3.9"
+python_requires = ">=3.10"
 description = "A Python module and command line parser for SPF and DMARC records"
 readme = "README.md"
 license = "Apache-2.0"