Fix syntax error

Change-Id: I046163dc7d441fa8aad8714af0e5caccf8252968
diff --git a/TestON/drivers/common/api/controller/onosrestdriver.py b/TestON/drivers/common/api/controller/onosrestdriver.py
index 2a60ba1..8dcc669 100755
--- a/TestON/drivers/common/api/controller/onosrestdriver.py
+++ b/TestON/drivers/common/api/controller/onosrestdriver.py
@@ -1645,7 +1645,7 @@
                     b = json.dumps( a )
                     return b
                 elif response[ 0 ] == 404:
-                    main.log.error( "Requested configuration doesn't exist: " +
+                    main.log.error( "Requested configuration doesn't exist: %s: %s" %
                                     ( response[ 0 ], response[ 1 ] ) )
                     return {}
                 else: