Give mapping views a usable repr.
diff --git a/Lib/_abcoll.py b/Lib/_abcoll.py
index 942a72c..40cc23e 100644
--- a/Lib/_abcoll.py
+++ b/Lib/_abcoll.py
@@ -371,6 +371,9 @@
     def __len__(self):
         return len(self._mapping)
 
+    def __repr__(self):
+        return '{0.__class__.__name__}({0._mapping!r})'.format(self)
+
 
 class KeysView(MappingView, Set):