use new sphinx modules
diff --git a/Doc/tools/sphinxext/suspicious.py b/Doc/tools/sphinxext/suspicious.py
index 9a2f601..ae11793 100644
--- a/Doc/tools/sphinxext/suspicious.py
+++ b/Doc/tools/sphinxext/suspicious.py
@@ -45,7 +45,7 @@
 import csv
 import re
 from docutils import nodes
-from sphinx.builder import Builder
+from sphinx.builders import Builder
 
 detect_all = re.compile(ur'''
     ::(?=[^=])|            # two :: (but NOT ::=)