docutils 0.22 doesn't work with sphinx-tabs

There is a pending fix upstream at
executablebooks/sphinx-tabs#207

Author: mr-c

dependencies/tox-docs-constraints.in

@@ -0,0 +1,17 @@
+###############################################################################
+#                                                                             #
+# This file is only meant to exclude broken dependency versions, not feature  #
+# dependencies.                                                               #
+#                                                                             #
+# GUIDELINES:                                                                 #
+#   1. Only list PyPI project versions that need to be excluded using `!=`    #
+#      and `<`.                                                               #
+#   2. It is allowed to have transitive dependency limitations in this file.  #
+#   3. Apply bare minimum constraints under narrow conditions, use            #
+#      environment markers if possible. E.g.  `; python_version < "3.12"`.    #
+#   4. Whenever there are no constraints, let the file and this header        #
+#      remain in Git.                                                         #
+#                                                                             #
+###############################################################################
+
+docutils < 0.22  # https://github.com/executablebooks/sphinx-tabs/pull/207

dependencies/tox-docs.in

@@ -1,3 +1,4 @@
+-c tox-docs-constraints.in  # limits known broken versions
 -r tests.in  # `sphinxcontrib-autodoc` will import all the files
 
 Sphinx >= 1.8.2

docs/changelog-fragments.d/811.packaging.rst

@@ -0,0 +1,4 @@
+Constrained the version of :pypi:`docutils` to before 0.22 so that the
+:pypi:`sphinx-tabs` plugin continues to work. Can be reverted once
+new release (>> 3.4.7) of :pypi:`sphinx-tabs` is made
+-- by :user:`mr-c`.