Handle DejaGnu ERROR messages.

Instead of silently ignoring them!

Change-Id: Ic48af21b4d60fa0ad166c973168a67d6ddae5ea8
diff --git a/testsuite/sum-1.txt b/testsuite/sum-1.txt
index 27c6235..b626a8c 100644
--- a/testsuite/sum-1.txt
+++ b/testsuite/sum-1.txt
@@ -62,3 +62,5 @@
 FAIL: test1-pass-and-fails
 
 FAIL: test1-fail-pass execution
+
+ERROR: (DejaGnu) proc "scan-dump-tree-not fail_test optimized 1" does not exist.