Update default merge failed error to mention CRD

The merge failure message is the same whether your change failed to
merge or it was one of its dependencies, including cross-repo
dependencies. Update the default error message for this to mention
the latter possibility so that contributors don't unnecessarily
rebase a dependent change which doesn't actually need it.

Change-Id: Ia17d9ab2a842574cf684b4ebb955dd2ec6e9ec3d
diff --git a/tests/test_scheduler.py b/tests/test_scheduler.py
index 3b59e3e..f330fb1 100755
--- a/tests/test_scheduler.py
+++ b/tests/test_scheduler.py
@@ -2951,9 +2951,10 @@
         self.registerJobs()
 
         self.assertEqual(
-            "Merge Failed.\n\nThis change was unable to be automatically "
-            "merged with the current state of the repository. Please rebase "
-            "your change and upload a new patchset.",
+            "Merge Failed.\n\nThis change or one of its cross-repo "
+            "dependencies was unable to be automatically merged with the "
+            "current state of its repository. Please rebase the change and "
+            "upload a new patchset.",
             self.sched.layout.pipelines['check'].merge_failure_message)
         self.assertEqual(
             "The merge failed! For more information...",