--- a/mercurial/ui.py	Sun Jun 25 14:41:12 2017 +0200
+++ b/mercurial/ui.py	Fri Jun 23 17:19:29 2017 +0200
@@ -1139,7 +1139,7 @@
 
         This function refers to input only; for output, see `ui.formatted()'.
         '''
-        i = self.configbool("ui", "interactive", None)
+        i = self.configbool("ui", "interactive")
         if i is None:
             # some environments replace stdin without implementing isatty
             # usually those are non-interactive