diff -r c95b2f40db7c -r 74802979dd9d mercurial/ui.py
--- a/mercurial/ui.py	Sun Oct 06 17:45:05 2019 -0400
+++ b/mercurial/ui.py	Sun Oct 06 17:59:15 2019 -0400
@@ -1966,7 +1966,7 @@
         if not self._loggers:
             return
         activeloggers = [
-            l for l in self._loggers.itervalues() if l.tracked(event)
+            l for l in pycompat.itervalues(self._loggers) if l.tracked(event)
         ]
         if not activeloggers:
             return