Pin docutils to older version

.readthedocs.yaml

@@ -0,0 +1,15 @@
+
+# SPDX-FileCopyrightText: 2021 ladyada for Adafruit Industries
+#
+# SPDX-License-Identifier: Unlicense
+# Read the Docs configuration file
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+# Required
+version: 2
+
+python:
+  version: "3.6"
+  install:
+    - requirements_file: docs/requirements.txt
+    - requirements_file: requirements.txt

docs/requirements.txt

@@ -0,0 +1 @@
+docutils<0.18