[Findit] Implementing swarming task error detection

appengine/findit/waterfall/trigger_base_swarming_task_pipeline.py

Index: appengine/findit/waterfall/trigger_base_swarming_task_pipeline.py
diff --git a/appengine/findit/waterfall/trigger_base_swarming_task_pipeline.py b/appengine/findit/waterfall/trigger_base_swarming_task_pipeline.py
index 720cb7784c5404ee2ab4a546cdfc6911a8e0a1a7..878f5c539c01b934d80c36e9c92c9954f89708bd 100644
--- a/appengine/findit/waterfall/trigger_base_swarming_task_pipeline.py
+++ b/appengine/findit/waterfall/trigger_base_swarming_task_pipeline.py
@@ -168,16 +168,20 @@ class TriggerBaseSwarmingTaskPipeline(BasePipeline):  # pragma: no cover.
         step_name, tests, iterations_to_rerun)
 
     # 3. Trigger a new Swarming task to re-run the failed tests.
-    task_id = swarming_util.TriggerSwarmingTask(new_request, http_client)
+    task_id, error = swarming_util.TriggerSwarmingTask(new_request, http_client)
 
-    # Save the task id.
+    # Update swarming task info.
     swarming_task = self._GetSwarmingTask(*call_args)
     swarming_task.task_id = task_id
     swarming_task.parameters['tests'] = tests
     swarming_task.parameters['iterations_to_rerun'] = iterations_to_rerun
     swarming_task.parameters['ref_name'] = swarming_util.GetTagValue(
         new_request.tags, 'ref_name')
-    swarming_task.put()
 
-    logging.info('A Swarming task was triggered:%s', task_id)
+    if error:
+      swarming_task.error = error
+    else:
+      logging.info('A Swarming task was triggered:%s', task_id)
+
+    swarming_task.put()
     return task_id