Merge remote branch 'cros/upstream' into master

scheduler/drone_manager.py

 import os, re, shutil, signal, subprocess, errno, time, heapq, traceback
 import common, logging
 from autotest_lib.client.common_lib import error, global_config
 from autotest_lib.scheduler import email_manager, drone_utility, drones
 from autotest_lib.scheduler import scheduler_config
 
 
 # results on drones will be placed under the drone_installation_directory in a
 # directory with this name
 _DRONE_RESULTS_DIR_SUFFIX = 'results'
@@ skipping 141 matching lines @@
         self._attached_files = {}
         # heapq of _DroneHeapWrappers
         self._drone_queue = []
 
 
     def initialize(self, base_results_dir, drone_hostnames,
                    results_repository_hostname):
         self._results_dir = base_results_dir
 
         for hostname in drone_hostnames:
-            drone = self._add_drone(hostname)
-            drone.call('initialize', self.absolute_path(''))
+            self._add_drone(hostname)
 
         if not self._drones:
             # all drones failed to initialize
             raise DroneManagerError('No valid drones found')
 
         self.refresh_drone_configs()
 
         logging.info('Using results repository on %s',
                      results_repository_hostname)
         self._results_drone = drones.get_drone(results_repository_hostname)
@@ skipping 24 matching lines @@
         """
         pidfile_timeout = global_config.global_config.get_config_value(
                 scheduler_config.CONFIG_SECTION, 'max_pidfile_refreshes',
                 type=int, default=2000)
         return pidfile_timeout
 
 
     def _add_drone(self, hostname):
         logging.info('Adding drone %s' % hostname)
         drone = drones.get_drone(hostname)
-        self._drones[drone.hostname] = drone
-        return drone
+        if drone:
+            self._drones[drone.hostname] = drone
+            drone.call('initialize', self.absolute_path(''))
 
 
     def _remove_drone(self, hostname):
         self._drones.pop(hostname, None)
 
 
     def refresh_drone_configs(self):
         """
         Reread global config options for all drones.
         """
@@ skipping 480 matching lines @@
 
 def instance():
     if _the_instance is None:
         _set_instance(DroneManager())
     return _the_instance
 
 
 def _set_instance(instance): # usable for testing
     global _the_instance
     _the_instance = instance