Update arthur-tf-a-gerrit-tforg-l1.yaml

Change-Id: I10424fd639123e2f504f6bcb21dfab567d2a4031
Signed-off-by: Arthur She <arthur.she@linaro.org>
diff --git a/arthur-scripts/parse_refspec.py b/arthur-scripts/parse_refspec.py
index 83fd30e..574d516 100755
--- a/arthur-scripts/parse_refspec.py
+++ b/arthur-scripts/parse_refspec.py
@@ -46,9 +46,8 @@
 changes.pop()
 
 if not changes:
-    raise Exception("Can not find anything.")
-
-if len(changes) > 1:
-   print_topic_tip(changes)
+    print("Warning: no changes found, returning empty string", file=sys.stderr)
+elif len(changes) > 1:
+    print_topic_tip(changes)
 else:
     print(changes[0]["currentPatchSet"]["ref"])