Make the linkcheck builder more resillient against transient network errors.
Not in a release yet, but landed on master: https://github.com/sphinx-doc/sphinx/pull/2312
We'll start at 2 retries and increase if it turns out to be insufficient to handle real world transient errors.
diff --git a/docs/conf.py b/docs/conf.py
index dcc9c62..643eddb 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -273,3 +273,7 @@
intersphinx_mapping = {'https://docs.python.org/3': None}
epub_theme = 'epub'
+
+# Retry requests in the linkcheck builder so that we're resillient against
+# transient network errors.
+linkcheck_retries = 2