--- a/mercurial/manifest.py	Mon Mar 13 21:58:43 2017 -0700
+++ b/mercurial/manifest.py	Mon Mar 13 12:40:14 2017 -0700
@@ -431,6 +431,8 @@
         # makes it easier for extensions to override.
         return len(self._lm) != 0
 
+    __bool__ = __nonzero__
+
     def __setitem__(self, key, node):
         self._lm[key] = node, self.flags(key, '')