Update Python support matrix

Twisted 23.10.0 dropped support for Python 3.7 and added support for
Python 3.12.

Twisted 23.8.0 added support for Python 3.11 and drops support for
PyPy <3.9.

Python 3.11 and 3.12 now exist.

.github/workflows/ci.yaml

@@ -51,7 +51,7 @@ jobs:
           ${{ runner.os }}-pip-docs-
           ${{ runner.os }}-pip-
 
-    - run: python -m pip install tox
+    - run: python -m pip install 'tox<4'
 
     - run: tox -q -e docs
 
@@ -63,15 +63,31 @@ jobs:
     continue-on-error: ${{ matrix.experimental }}
     strategy:
       matrix:
-          python-version: ["3.7", "3.8", "3.9", "3.10", "pypy-3.8", "pypy-3.9"]
+          # Python versions common to lowest and latest
+          python-version: ["3.8", "3.9", "3.10", "3.11", "pypy-3.9"]
           twisted-version: ["lowest", "latest"]
           experimental: [false]
 
           include:
-          - python-version: "3.8"
-            twisted-version: "trunk"
-            experimental: true
+          # Pythons too old for latest
+          - python-version: "3.7"
+            twisted-version: "lowest"
+            experimental: false
+
+          - python-version: "pypy-3.8"
+            twisted-version: "lowest"
+            experimental: false
+
+          # Pythons too new for lowest
+          - python-version: "3.12"
+            twisted-version: "latest"
+            experimental: false
+
+          - python-version: "pypy-3.10"
+            twisted-version: "latest"
+            experimental: false
 
+          # Experimental trunk build
           - python-version: "3.9"
             twisted-version: "trunk"
             experimental: true
@@ -101,8 +117,11 @@ jobs:
           "3.8": "py38",
           "3.9": "py39",
           "3.10": "py310",
+          "3.11": "py311",
+          "3.12": "py312",
           "pypy-3.8": "pypy3",
           "pypy-3.9": "pypy3",
+          "pypy-3.10": "pypy3",
         }
         factor = table["${{ matrix.python-version }}"]
         print("::set-output name=value::" + factor)

changelog.d/374.feature.rst

@@ -0,0 +1 @@
+PyPy 3.10 is now supported.

changelog.d/374.removal.rst

@@ -0,0 +1 @@
+Support for PyPy 3.8, which has reached end of support, is deprecated. This is the last release with support for PyPy 3.8.

tox.ini

@@ -1,8 +1,8 @@
 [tox]
 envlist =
     py37-twisted_lowest,
-    {pypy3,py37,py38,py39,py310}-twisted_latest,
-    {pypy3,py37,py38,py39,py310}-twisted_trunk,
+    {pypy3,py38,py39,py310,py311,py312}-twisted_latest,
+    {pypy3,py38,py39,py310,py311,py312}-twisted_trunk,
     twine, check-manifest, flake8, docs, coverage-report
 isolated_build = true
 
@@ -60,7 +60,7 @@ commands =
     sphinx-build -b html . html
 
 [testenv:coverage-report]
-depends = pypy3,py37,py38,py39
+depends = pypy3,py37,py38,py39,py310,py311,py312
 commands =
     coverage combine
     coverage report