[Findit] Record error if swarming task completes with exit_code as 2.

appengine/findit/waterfall/test/swarming_util_test.py

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import collections
 import json
 import os
 import urllib
 import zlib
 
@@ skipping 560 matching lines @@
         'valid': True
     }
 
     self.assertEqual(expected_failure_log, failure_log)
 
   def testGetTagValueInvalidTag(self):
     tags = ['a:1', 'b:2']
     self.assertIsNone(swarming_util.GetTagValue(tags, 'c'))
 
   def testGenerateIsolatedDataOutputsrefNone(self):
-    self.assertEqual({}, swarming_util._GenerateIsolatedData(None))
+    self.assertEqual({}, swarming_util._GenerateIsolatedData(None))
+
+  def testFetchOutputJsonInfoFromIsolatedServerReturnNone(self):
+    self.assertIsNone(swarming_util._FetchOutputJsonInfoFromIsolatedServer(
+        None, self.http_client))