ART: Logging levels for Checker

Small patch which enables Checker to print errors but not info
messages as opposed to the current all or nothing. This is useful for
running Checker with run-test.

Change-Id: I500ded0db4f83ed9bbdef9c1f7b1eb18a90d7f0e
diff --git a/tools/checker_test.py b/tools/checker_test.py
index 3c659c2..1466b93 100755
--- a/tools/checker_test.py
+++ b/tools/checker_test.py
@@ -457,5 +457,5 @@
                                                          ("def", CheckVariant.DAG) ])) ])
 
 if __name__ == '__main__':
-  checker.Logger.SilentMode = True
+  checker.Logger.Verbosity = checker.Logger.Level.NoOutput
   unittest.main()