Add python 3.13 to CI

Adding pre-release versions of python lets us identify issues in
advance.

.github/workflows/future_python.yml

@@ -0,0 +1,48 @@
+name: Test pre-release versions of python
+
+on:
+    push:
+    pull_request:
+
+jobs:
+    build:
+        runs-on: ubuntu-24.04
+        name: "python ${{ matrix.python-version }} on ${{ matrix.backend }}"
+        continue-on-error: true
+        strategy:
+            matrix:
+                # If you change one of these, be sure to update:
+                # - /tox.ini:[gh-actions]
+                # - /setup.cfg:[mypy]
+                # If adding new python versions, consider also updating
+                # python version in .readthedocs.yaml
+                # TODO: Add back pypy here and in release.yml once:
+                # https://github.com/pypy/pypy/issues/4956 is resolved
+                python-version: ['3.13']
+                backend: ['x11', 'wayland']
+        steps:
+            - uses: actions/checkout@v4
+            - name: Set up python ${{ matrix.python-version }}
+              uses: actions/setup-python@v5
+              with:
+                  python-version: ${{ matrix.python-version }}
+                  allow-prereleases: true
+            - name: Install dependencies
+              run: |
+                sudo apt update
+                # Any Wayland-specific Ubuntu system dependencies should be installed from ./scripts/ubuntu_wayland_setup
+                sudo apt install --no-install-recommends \
+                  libdbus-1-dev libgirepository1.0-dev gir1.2-gtk-3.0 gir1.2-notify-0.7 gir1.2-gudev-1.0 graphviz \
+                  imagemagick git xserver-xephyr xterm xvfb dbus-x11 libnotify-bin \
+                  libxcb-composite0-dev libxcb-icccm4-dev libxcb-res0-dev libxcb-render0-dev libxcb-res0-dev \
+                  libxcb-xfixes0-dev vlc volumeicon-alsa libxkbcommon-dev python-gi-dev tox libcairo2-dev
+                pip -q install --break-system-packages tox-gh-actions
+            - name: Install wayland
+              if: ${{ matrix.backend == 'wayland' }}
+              run: bash -x ./scripts/ubuntu_wayland_setup
+            - name: Run Tests
+              run: |
+                [ "$(grep -c -P '\t' CHANGELOG)" = "0" ]
+                tox
+              env:
+                BACKEND: ${{ matrix.backend }}

tox.ini

@@ -4,7 +4,7 @@ skipsdist=True
 minversion = 4.0.12
 envlist =
     # Python environments with specific backend
-    py{py3,310,311,312}-{x11,wayland}
+    py{py3,310,311,312,313}-{x11,wayland}
     docs,
     packaging-{x11,wayland},
     # For running pytest locally
@@ -35,7 +35,7 @@ commands =
     !x11: {toxinidir}/scripts/ffibuild
 
 # These are the environments that should be triggered by Github Actions
-[testenv:py{py3,310,311,312}-{wayland,x11}]
+[testenv:py{py3,310,311,312,313}-{wayland,x11}]
 # This is required in order to get UTF-8 output inside of the subprocesses
 # that our tests use.
 setenv = LC_CTYPE = en_US.UTF-8
@@ -54,8 +54,8 @@ commands =
     # pypy3 is very slow when running coverage reports so we skip it
     pypy3-x11: python3 -m pytest --backend=x11 {posargs}
     pypy3-wayland: python3 -m pytest --backend=wayland {posargs}
-    py3{10,11,12}-x11: coverage run -m pytest --backend=x11 {posargs}
-    py3{10,11,12}-wayland: coverage run -m pytest --backend=wayland {posargs}
+    py3{10,11,12,13}-x11: coverage run -m pytest --backend=x11 {posargs}
+    py3{10,11,12,13}-wayland: coverage run -m pytest --backend=wayland {posargs}
 
     # Coverage is only run via GithubActions
     # Coverage runs tests in parallel so we need to combine results into a single file
@@ -125,6 +125,7 @@ python =
     3.10: py310
     3.11: py311
     3.12: py312, packaging
+    3.13: py313
 
 [gh-actions:env]
 BACKEND =