additional fixes suggested by @anba

test/harness/sta.js

@@ -13,7 +13,7 @@ function Test262Error(message) {
 }
 
 Test262Error.prototype.toString = function () {
-    return "Test262 Error: " + this.message;
+    return "Test262Error: " + this.message;
 };
 
 var $ERROR;

tools/packaging/test262.py

@@ -209,10 +209,15 @@ class TestResult(object):
     if self.case.IsAsyncTest():		
        return self.AsyncHasFailed() or self.HasFailed()
     elif self.case.IsNegative():      
-       return not (self.HasFailed() and self.case.NegativeMatch(self.stderr))
+       return not (self.HasFailed() and self.case.NegativeMatch(self.GetErrorOutput()))
     else:      
        return self.HasFailed()
 
+  def GetErrorOutput(self):
+    if len(self.stderr) != 0:
+      return self.stderr
+    return self.stdout
+
 
 class TestCase(object):