doc/devguide: language fix for sphinx

Newer Sphinx does not allow a language of none, set to "en" like we do
for the user guide.

diff --git a/doc/devguide/conf.py b/doc/devguide/conf.py
index 8b727a8aa381e033e0a6555d97962862256d7a49..39ba4e66309e5d76310d02d48a128f734403aef3 100644 (file)
--- a/doc/devguide/conf.py
+++ b/doc/devguide/conf.py
@@ -74,7 +74,7 @@ release = version
 #
 # This is also used if you do content translation via gettext catalogs.
 # Usually you set "language" from the command line for these cases.
-language = None
+language = 'en'
 
 # There are two options for replacing |today|: either, you set today to some
 # non-false value, then it is used: