Support Python 3.13, drop Python 3.9

Python 3.9 has reached end-of-life, so we can raise our limited API
compatibility

.github/workflows/tests.yml

@@ -9,7 +9,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: 3.8
+          python-version: 3.9
       - name: Build documentation
         env:
           READTHEDOCS: "True"
@@ -23,7 +23,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: 3.8
+          python-version: 3.9
       - name: Install packages
         run: pip install check-manifest mypy ruff types-certifi types-pyopenssl
       - name: Run linters
@@ -52,11 +52,11 @@ jobs:
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
         python:
+          - "3.13"
           - "3.12"
           - "3.11"
           - "3.10"
           - "3.9"
-          - "3.8"
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
@@ -96,7 +96,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-python@v5
         with:
-          python-version: 3.8
+          python-version: 3.9
       - name: Build source package
         run: |
           pip install -U build

pyproject.toml

@@ -19,11 +19,11 @@ classifiers = [
     "Operating System :: OS Independent",
     "Programming Language :: Python",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.8",
     "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",
     "Topic :: Internet :: WWW/HTTP",
 ]
 dependencies = [

setup.py

@@ -16,7 +16,7 @@ def get_tag(self):
         python, abi, plat = super().get_tag()
 
         if python.startswith("cp"):
-            return "cp38", "abi3", plat
+            return "cp39", "abi3", plat
 
         return python, abi, plat