diff -r 949d496c4e96 -r 60a1fbdbbed3 src/source/conf.py
--- a/src/source/conf.py	Wed May 09 17:33:41 2018 +0200
+++ b/src/source/conf.py	Tue May 15 18:31:37 2018 +0200
@@ -107,7 +107,7 @@
 #
 # 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'
 
 # List of patterns, relative to source directory, that match files and
 # directories to ignore when looking for source files.
@@ -117,10 +117,12 @@
 # The name of the Pygments (syntax highlighting) style to use.
 pygments_style = 'sphinx'
 
+# The default language to highlight source code in.
+highlight_language = 'python3'
+
 # If true, `todo` and `todoList` produce output, else they produce nothing.
 todo_include_todos = False
 
-
 # -- Options for HTML output ----------------------------------------------
 
 # The theme to use for HTML and HTML Help pages.  See the documentation for
@@ -241,5 +243,6 @@
 
 
 def setup(app):
+
     app.add_stylesheet('css/custom.css')