--- a/mercurial/error.py	Thu Apr 13 22:19:28 2017 -0700
+++ b/mercurial/error.py	Fri Apr 14 00:33:56 2017 -0700
@@ -252,3 +252,6 @@
 
 class CorruptedState(Exception):
     """error raised when a command is not able to read its state from file"""
+
+class RichIOError(Abort):
+    """An IOError that can also have a hint attached."""