[Findit] Update try-job result in a transaction and fix bugs in unittests.

appengine/findit/waterfall/monitor_try_job_pipeline.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.
 
 from datetime import datetime
 import json
 import time
 
+from google.appengine.ext import ndb
+
 from common.pipeline_wrapper import BasePipeline
 from common.pipeline_wrapper import pipeline
 from common.waterfall import buildbucket_client
 from common.waterfall import try_job_error
 from common.waterfall.buildbucket_client import BuildbucketBuild
 from model import analysis_status
 from model.wf_try_job import WfTryJob
 from model.wf_try_job_data import WfTryJobData
 from waterfall import waterfall_config
 from waterfall.try_job_type import TryJobType
@@ skipping 111 matching lines @@
 
     error_dict, error_code = MonitorTryJobPipeline._GetError(
         buildbucket_response, buildbucket_error, timed_out)
 
     if error_dict:
       try_job_data.error = error_dict
       try_job_data.error_code = error_code
 
     try_job_data.put()
 
+  @ndb.transactional
   def _UpdateTryJobResult(
       self, status, master_name, builder_name, build_number, try_job_type,
       try_job_id, try_job_url, result_content=None):
     """Updates try job result based on responsed try job status and result."""
     result = {
         'report': result_content,
         'url': try_job_url,
         'try_job_id': try_job_id,
     }
 
@@ skipping 81 matching lines @@
           already_set_started = True
 
       if time.time() > deadline:  # pragma: no cover
         self._UpdateTryJobMetadata(try_job_data, start_time, build, error, True)
         # Explicitly abort the whole pipeline.
         raise pipeline.Abort(
             'Try job %s timed out after %d hours.' % (
                 try_job_id, timeout_hours))
 
       time.sleep(pipeline_wait_seconds)  # pragma: no cover