added id to KeyError for get and set on Components (#112)

Author: ned2

dash/development/base_component.py

@@ -103,7 +103,7 @@ def _get_set_or_delete(self, id, operation, new_item=None):
 
         # The end of our branch
         # If we were in a list, then this exception will get caught
-        raise KeyError
+        raise KeyError(id)
 
     # Supply ABC methods for a MutableMapping:
     # - __getitem__