From 447b6c866f0741bb68c92dc925a65fb15bfe7995 Mon Sep 17 00:00:00 2001
From: Carlton Gibson <carlton@noumenal.es>
Date: Wed, 3 Nov 2021 18:35:27 +0100
Subject: [PATCH] Refs #33247 -- Corrected configuration for Read The Docs.

This pins Sphinx version, because the default Sphinx version used by
RTD is not compatible with Python 3.8+.

This also, sets Python 3.8 for RTD builds which is compatible with all
current versions of Django.

Thanks to Mariusz Felisiak for the suggestion.
---
 .readthedocs.yml      | 9 ++++++---
 docs/requirements.txt | 2 +-
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/.readthedocs.yml b/.readthedocs.yml
index d6ca0316b3..18f81acab2 100644
--- a/.readthedocs.yml
+++ b/.readthedocs.yml
@@ -1,17 +1,20 @@
 # Configuration for the Read The Docs (RTD) builds of the documentation.
 # Ref: https://docs.readthedocs.io/en/stable/config-file/v2.html
-# Note python.install.requirements is not currently required, as Sphinx is
-# preinstalled and spelling checks not performed by RTD.
+# The python.install.requirements pins the version of Sphinx used.
 version: 2
 
 build:
   os: ubuntu-20.04
   tools:
-    python: "3.10"
+    python: "3.8"
 
 sphinx:
   configuration: docs/conf.py
 
+python:
+  install:
+    - requirements: docs/requirements.txt
+
 formats:
   - epub
   - pdf
diff --git a/docs/requirements.txt b/docs/requirements.txt
index e95ceeec27..6ea1372680 100644
--- a/docs/requirements.txt
+++ b/docs/requirements.txt
@@ -1,3 +1,3 @@
 pyenchant
-sphinx
+Sphinx>=3.1.0
 sphinxcontrib-spelling