suppress messages for PresubmitAddText results

tests/presubmit_unittest.py

Index: tests/presubmit_unittest.py
diff --git a/tests/presubmit_unittest.py b/tests/presubmit_unittest.py
index e61ca6cfa5ae437b0f6d0f5640da1a3f3d2af6f4..80a6e8dd0e3a3251816a0691898d1bac122172b7 100755
--- a/tests/presubmit_unittest.py
+++ b/tests/presubmit_unittest.py
@@ -1045,17 +1045,23 @@ class OuputApiUnittest(PresubmitTestsBase):
   def testOutputApiBasics(self):
     self.mox.ReplayAll()
     self.failUnless(presubmit.OutputApi.PresubmitError('').IsFatal())
+    self.failUnless(presubmit.OutputApi.PresubmitError('').IsMessage())
     self.failIf(presubmit.OutputApi.PresubmitError('').ShouldPrompt())
 
     self.failIf(presubmit.OutputApi.PresubmitPromptWarning('').IsFatal())
     self.failUnless(
         presubmit.OutputApi.PresubmitPromptWarning('').ShouldPrompt())
+    self.failUnless(
+        presubmit.OutputApi.PresubmitPromptWarning('').IsMessage())
 
     self.failIf(presubmit.OutputApi.PresubmitNotifyResult('').IsFatal())
     self.failIf(presubmit.OutputApi.PresubmitNotifyResult('').ShouldPrompt())
+    self.failUnless(
+        presubmit.OutputApi.PresubmitNotifyResult('foo').IsMessage())
 
     self.failIf(presubmit.OutputApi.PresubmitAddText('foo').IsFatal())
     self.failIf(presubmit.OutputApi.PresubmitAddText('foo').ShouldPrompt())
+    self.failIf(presubmit.OutputApi.PresubmitAddText('foo').IsMessage())
 
     # TODO(joi) Test MailTextResult once implemented.