Support revisions with str type for try jobs.

model.py

 # Copyright (c) 2012 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.
 
 """Defines the PersistentMixIn utility class to easily convert classes to and
 from dict for serialization.
 
 This class is aimed at json-compatible serialization, so it supports the limited
 set of structures supported by json; strings, numbers as int or float, list and
 dictionaries.
@@ skipping 222 matching lines @@
     for item in dir(cls):
       if item.startswith('_'):
         continue
       item_value = getattr(cls, item)
       if isinstance(item_value, type):
         item_value = (item_value,)
       if not isinstance(item_value, tuple):
         continue
       if not all(i is None or i.__class__ == type for i in item_value):
         continue
-      if any(i is str for i in item_value):
-        raise TypeError(
-            '%s is type \'str\' which is currently not supported' % item)
       item_value = tuple(
           f if f is not None else None.__class__ for f in item_value)
       persistent_members_cache[item] = item_value
     return persistent_members_cache
 
   @staticmethod
   def _get_subclass(typename):
     """Returns the PersistentMixIn subclass with the name |typename|."""
     subclass = None
     if PersistentMixIn.__persistent_classes_cache is not None:
@@ skipping 141 matching lines @@
 def save_to_json_file(filename, obj):
   """Save one object in a JSON file."""
   try:
     old = filename + '.old'
     if os.path.exists(filename):
       os.rename(filename, old)
   finally:
     with open(filename, 'wb') as f:
       json.dump(obj.as_dict(), f, sort_keys=True, indent=2)
       f.write('\n')