Fixes RunPythonUnitTests output.

presubmit_canned_checks.py

Index: presubmit_canned_checks.py
diff --git a/presubmit_canned_checks.py b/presubmit_canned_checks.py
index f31b1687a352e306dd1bd415d31e702a44c416e2..d020c165925e7a51d969c23f85fc6a6e009d1a20 100755
--- a/presubmit_canned_checks.py
+++ b/presubmit_canned_checks.py
@@ -169,9 +169,11 @@ def RunPythonUnitTests(input_api, output_api, unit_tests):
       outputs.append(message_type("Failed to load %s" % unit_test,
                                   long_text=input_api.traceback.format_exc()))
 
-  results = input_api.unittest.TextTestRunner(verbosity=0).run(
+  buffer = input_api.cStringIO.StringIO()
+  results = input_api.unittest.TextTestRunner(stream=buffer, verbosity=0).run(
       input_api.unittest.TestSuite(tests_suite))
   if not results.wasSuccessful():
     outputs.append(message_type("%d unit tests failed." %
-                                (len(results.failures) + len(results.errors))))
+                                (len(results.failures) + len(results.errors)),
+                                long_text=buffer.getvalue()))
   return outputs