Add Python 3.10 support (#1334)

* Add Python 3.10 support

* Add new Sphinx versions to tox test matrix, but do not allow docutils >= 0.17 on Sphinx>=4.3

* Stop py2 and py27 support from sphinxlatest because of build breakage

* Circle CI: Repeat sphinx versions for Python 2.7 (pending adjustments)

* tox.ini config: Ensure that we are getting the expected Sphinx version

* Set sphinx versions for Python 3.10

.circleci/config.yml

@@ -71,12 +71,22 @@ jobs:
     steps:
       - run-tox:
           version: py39
+  py310:
+    docker:
+      - image: 'cimg/python:3.10'
+    steps:
+      - run-tox:
+          version: py310
+          sphinx-version: "42,43,44,45,50,51,latest"
 
 workflows:
   version: 2
   tests:
     jobs:
       - build
+      - py310:
+          requires:
+            - build
       - py39:
           requires:
             - build

setup.cfg

@@ -24,6 +24,7 @@ classifiers =
   Programming Language :: Python :: 3.7
   Programming Language :: Python :: 3.8
   Programming Language :: Python :: 3.9
+  Programming Language :: Python :: 3.10
   Operating System :: OS Independent
   Topic :: Documentation
   Topic :: Software Development :: Documentation

tox.ini

@@ -2,6 +2,7 @@
 envlist =
     py{2,27}-sphinx{16,17,18,20,21,22,23,24,30,31,32,33,34,35,40,41,42,43,44,45,50,51}{-html4,-html5,}{-qa,}
     py{3,36,37,38,39}-sphinx{16,17,18,20,21,22,23,24,30,31,32,33,34,35,40,41,42,43,44,45,50,51,latest}{-html4,-html5,}{-qa,}
+    py{310}-sphinx{42,43,44,45,50,51,latest}{-html4,-html5,}{-qa,}
 
 [testenv]
 setev =