Use HTTPS for a number of URLs in the docs
diff --git a/docs/conf.py b/docs/conf.py
index b70114d..fc16b38 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -268,6 +268,6 @@
 # texinfo_show_urls = 'footnote'
 
 # Example configuration for intersphinx: refer to the Python standard library.
-intersphinx_mapping = {'http://docs.python.org/': None}
+intersphinx_mapping = {'https://docs.python.org/': None}
 
 epub_theme = 'epub'