Move recipe engine to third_party/recipe_engine.

scripts/slave/recipe_modules/gsutil/api.py

 # Copyright 2013 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.
 
 import re
 
-from slave import recipe_api
-from slave import recipe_util
+from recipe_engine import recipe_api
+from recipe_engine import recipe_util
 
 class GSUtilApi(recipe_api.RecipeApi):
   def __call__(self, cmd, name=None, use_retry_wrapper=True, version='3.25',
                **kwargs):
     """A step to run arbitrary gsutil commands.
 
     Note that this assumes that gsutil authentication environment variables
     (AWS_CREDENTIAL_FILE and BOTO_CONFIG) are already set, though if you want to
     set them to something else you can always do so using the env={} kwarg.
 
@@ skipping 178 matching lines @@
         'Content-Language',
         'Content-MD5',
         'Content-Type',
     ):
       return name
 
     # Add provider prefix
     if not provider_prefix:
       provider_prefix = 'x-goog-meta'
     return '%s-%s' % (provider_prefix, name)