Tests/CI: use Python 3.13 by default

Upgrade from Python 3.12 to 3.13 for running tox
and for generic jobs like lint and doc.

Author: medmunds

.github/workflows/release.yml

@@ -31,7 +31,7 @@ jobs:
       - name: Setup Python
         uses: actions/setup-python@v5
         with:
-          python-version: "3.12"
+          python-version: "3.13"
 
       - name: Install build requirements
         run: |

.github/workflows/test.yml

@@ -19,6 +19,12 @@ jobs:
     steps:
       - name: Get code
         uses: actions/checkout@v4
+      - name: Setup default Python
+        # Change default Python version to something consistent
+        # for installing/running tox
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.13"
       - name: Install tox-gh-matrix
         run: |
           python -m pip install 'tox<4' 'tox-gh-matrix<0.3'
@@ -52,7 +58,7 @@ jobs:
         # for installing/running tox
         uses: actions/setup-python@v5
         with:
-          python-version: "3.12"
+          python-version: "3.13"
       - name: Install tox
         run: |
           set -x

tox.ini

@@ -83,7 +83,7 @@ passenv =
     ANYMAIL_TEST_*
 
 [testenv:lint]
-basepython = python3.12
+basepython = python3.13
 skip_install = true
 passenv =
     CONTINUOUS_INTEGRATION
@@ -104,7 +104,7 @@ commands =
     pre-commit run --all-files
 
 [testenv:docs]
-basepython = python3.12
+basepython = python3.13
 passenv =
     CONTINUOUS_INTEGRATION
     GOOGLE_ANALYTICS_ID