Make bisect not break when buildbucket.get fails.

scripts/slave/recipe_modules/auto_bisect/revision_state.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.
 
 """An interface for holding state and result of revisions in a bisect job.
 
 When implementing support for tests other than perf, one should extend this
 class so that the bisect module and recipe can use it.
 
 See perf_revision_state for an example.
@@ skipping 279 matching lines @@
       api = self.bisector.api
       self.build_archived = api.gsutil_file_exists(self.build_url)
 
     if self.bisector.dummy_builds:
       self.build_archived = self.in_progress
 
     return self.build_archived
 
   def _is_build_failed(self):
     api = self.bisector.api
-    result = api.m.buildbucket.get_build(
-        self.build_id,
-        api.m.service_account.get_json_path(api.SERVICE_ACCOUNT),
-        step_test_data=lambda: api.m.json.test_api.output_stream(
-            {'build': {'result': 'SUCCESS', 'status': 'COMPLETED'}}
-        ))
+    try:
+      result = api.m.buildbucket.get_build(
+          self.build_id,
+          api.m.service_account.get_json_path(api.SERVICE_ACCOUNT),
+          step_test_data=lambda: api.m.json.test_api.output_stream(
+              {'build': {'result': 'SUCCESS', 'status': 'COMPLETED'}}
+          ))
+    except api.m.step.StepFailure:  # pragma: no cover
+      # If the check fails, we cannot assume that the build is failed.

[prasadv1, 2016/10/21 21:37:17]

What should happen when buildbucket.get() fails and also build is failed?

+      return False
     return (result.stdout['build']['status'] == 'COMPLETED' and
             result.stdout['build'].get('result') != 'SUCCESS')
 
   def _results_available(self):
     """Checks if the results for the test job have been uploaded."""
     api = self.bisector.api
     result = api.gsutil_file_exists(self.test_results_url)
     if self.bisector.dummy_builds:
       return self.in_progress
     return result  # pragma: no cover
@@ skipping 253 matching lines @@
     else:
       next_revision_to_test.retest()
 
   def __repr__(self):
     if self.overall_return_code is not None:
       return ('RevisionState(rev=%s, values=%r, overall_return_code=%r, '
               'std_dev=%r)') % (self.revision_string(), self.values,
                                 self.overall_return_code, self.std_dev)
     return ('RevisionState(rev=%s, values=%r, mean_value=%r, std_dev=%r)' % (
         self.revision_string(), self.values, self.mean_value, self.std_dev))