Use a standard DBus error for not found

Change-Id: I93c086c872aa7ff7d59af366b93fd7948fe8d1bf
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/obmc/mapper/bindings.py b/obmc/mapper/bindings.py
index f193a50..1f4139a 100644
--- a/obmc/mapper/bindings.py
+++ b/obmc/mapper/bindings.py
@@ -23,7 +23,7 @@
 MAPPER_NAME = 'org.openbmc.ObjectMapper'
 MAPPER_IFACE = MAPPER_NAME
 MAPPER_PATH = '/org/openbmc/ObjectMapper'
-MAPPER_NOT_FOUND = MAPPER_NAME + '.Error.NotFound'
+MAPPER_NOT_FOUND = 'org.freedesktop.DBus.Error.FileNotFound'
 
 
 class Mapper: