Backport PR matplotlib#23830: Start testing on Python 3.11

Author: QuLogic

.github/workflows/tests.yml

@@ -48,6 +48,8 @@ jobs:
           - os: ubuntu-20.04
             python-version: '3.10'
             extra-requirements: '-r requirements/testing/extra.txt'
+          - os: ubuntu-20.04
+            python-version: '3.11.0-rc.1'
           - os: macos-latest
             python-version: 3.8
 

setup.py

@@ -286,6 +286,7 @@ def make_release_tree(self, base_dir, files):
         'Programming Language :: Python :: 3.8',
         'Programming Language :: Python :: 3.9',
         'Programming Language :: Python :: 3.10',
+        'Programming Language :: Python :: 3.11',
         'Topic :: Scientific/Engineering :: Visualization',
     ],