compare_dg_tests.pl: Print an error instead of a warning
when pass ratio is too low.

Indeed, this results in an error return-code, and printing
a warning is confusing.

Change-Id: Ibd2b84173a79de39334f4b67b55513b893ba467d
diff --git a/compare_dg_tests.pl b/compare_dg_tests.pl
index 2bccb7f..cc45605 100755
--- a/compare_dg_tests.pl
+++ b/compare_dg_tests.pl
@@ -463,11 +463,11 @@
        printf "    RES PASS ratio: %.2f\n", $res_ratio;
        if ($ref_ratio < $ratio_thresh)
        {
-	   printf "    ***** WARNING: REF PASS ratio is abnormally low *****\n";
+	   printf "    ***** ERROR: REF PASS ratio is abnormally low *****\n";
        }
        if ($res_ratio < $ratio_thresh)
        {
-	   printf "    ***** WARNING: RES PASS ratio is abnormally low *****\n";
+	   printf "    ***** ERROR: RES PASS ratio is abnormally low *****\n";
        }
 
        # If both PASS and FAIL EXEC tests are zero, assume there is no
diff --git a/testsuite/expected-1-2.txt b/testsuite/expected-1-2.txt
index 9aa53c4..2b8b883 100644
--- a/testsuite/expected-1-2.txt
+++ b/testsuite/expected-1-2.txt
@@ -16,8 +16,8 @@
 
     REF PASS ratio: 0.29
     RES PASS ratio: 0.48
-    ***** WARNING: REF PASS ratio is abnormally low *****
-    ***** WARNING: RES PASS ratio is abnormally low *****
+    ***** ERROR: REF PASS ratio is abnormally low *****
+    ***** ERROR: RES PASS ratio is abnormally low *****
     ***** ERROR: No REF execution test PASSed. Check execution engine configuration. *****
     ***** WARNING: No RES execution test FAILed. Check execution engine configuration. *****