Change models.py to use typed class members instead of a list of strings.

verification/base.py

 # coding=utf8
 # 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 base classes for pending change verification classes."""
 
 import model
 
 
 # Verifier state in priority level.
@@ skipping 10 matching lines @@
   """Exception to be raised when a pending item should be discarded."""
 
   def __init__(self, pending, status):
     super(DiscardPending, self).__init__(status)
     self.pending = pending
     self.status = status
 
 
 class Verified(model.PersistentMixIn):
   """A set of verifications that are for a specific patch."""
-  persistent = [
-      'verifications',
-  ]
-
-  def __init__(self):
-    super(Verified, self).__init__()
-    self.verifications = {}
+  verifications = dict
 
   def pending_name(self):
     raise NotImplementedError()
 
   def get_state(self):
     """Returns the combined state of all the verifiers for this item.
 
     Use priority with the states: IGNORED > FAILED > PROCESSING > SUCCEEDED.
     """
     # If there's an error message, it failed.
@@ skipping 18 matching lines @@
     out = (i.error_message for i in self.verifications.itervalues())
     return '\n\n'.join(filter(None, out))
 
   def apply_patch(self, context, prepare):
     """Applies a patch from the codereview tool to the checkout."""
     raise NotImplementedError()
 
 
 class IVerifierStatus(model.PersistentMixIn):
   """Interface for objects in Verified.verifications dictionary."""
-  persistent = [
-      'error_message'
-  ]
-
-  def __init__(self, error_message=None):
-    super(IVerifierStatus, self).__init__()
-    self.error_message = error_message
+  error_message = (None, str)
 
   def get_state(self):
     """See Verified.get_state()."""
     raise NotImplementedError()
 
   def postpone(self):  # pylint: disable=R0201
     """See Verified.postpone()."""
     return False
 
 
 class SimpleStatus(IVerifierStatus):
   """Base class to be used for simple true/false verifiers."""
-  persistent = IVerifierStatus.persistent + [
-      'state',
-  ]
+  state = int
 
-  def __init__(self, state=PROCESSING, error_message=None):
-    super(SimpleStatus, self).__init__(error_message)
-    self.state = state
+  def __init__(self, state=PROCESSING, **kwargs):
+    super(SimpleStatus, self).__init__(state=state, **kwargs)
 
   def get_state(self):
     return self.state
 
 
 class Verifier(object):
   name = None
 
   def __init__(self):
     assert self.name is not None
@@ skipping 30 matching lines @@
   When verify() is called, it is guaranteed that the patch is applied on the
   checkout.
   """
   def __init__(self, context_obj):
     super(VerifierCheckout, self).__init__()
     self.context = context_obj
 
   def send_status(self, pending, data):
     self.context.status.send(
         pending, {'verification': self.name, 'payload': data})