swarming: add transaction_id to tasks.new request

appengine/swarming/server/task_request.py

 # coding: utf-8
 # Copyright 2014 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 """Tasks definition.
 
 Each user request creates a new TaskRequest. The TaskRequest instance saves the
 metadata of the request, e.g. who requested it, when why, etc. It links to the
 actual data of the request in a TaskProperties. The TaskProperties represents
@@ skipping 641 matching lines @@
     This is used for:
       * Read access: ability to read the task info and logs.
       * Write access: ability to cancel the task.
 
     Warning: This function looks at the current Authentication context.
     """
     return (
         acl.is_privileged_user() or
         self.authenticated == auth.get_current_identity())
 
-  def to_dict(self):
+  def to_dict(self, exclude=None):
     """Converts properties_hash to hex so it is json serializable."""
     # to_dict() doesn't recurse correctly into ndb.LocalStructuredProperty!
-    out = super(TaskRequest, self).to_dict(
-        exclude=['pubsub_auth_token', 'properties', 'service_account_token'])
+    exclude = (exclude or [])[:]
+    exclude.extend(['pubsub_auth_token', 'properties', 'service_account_token'])
+    out = super(TaskRequest, self).to_dict(exclude=exclude)
     out['properties'] = self.properties.to_dict()
     properties_hash = out['properties_hash']
     out['properties_hash'] = (
         properties_hash.encode('hex') if properties_hash else None)
     return out
 
   def _pre_put_hook(self):
     """Adds automatic tags."""
     super(TaskRequest, self)._pre_put_hook()
     self.properties._pre_put_hook()
@@ skipping 265 matching lines @@
   init_new_request(request, allow_high_priority, original_secret_bytes)
   return request
 
 
 def validate_priority(priority):
   """Throws ValueError if priority is not a valid value."""
   if 0 > priority or MAXIMUM_PRIORITY < priority:
     raise datastore_errors.BadValueError(
         'priority (%d) must be between 0 and %d (inclusive)' %
         (priority, MAXIMUM_PRIORITY))