+from bt2 import error as bt2_error
+
+
+class UnknownObject(Exception):
+ """
+ Raised when a component class handles a query for an object it doesn't
+ know about.
+ """
+
+ pass
+
+
+class _OverflowError(bt2_error._Error, OverflowError):
+ pass
+
+
+class TryAgain(Exception):
+ pass
+
+
+class Stop(StopIteration):
+ pass