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

verification/base.py

Index: verification/base.py
diff --git a/verification/base.py b/verification/base.py
index 4ca196580d32324412c1932e90816db39b0be136..7f2349eb045b5f717cb7d02667190fde49297835 100644
--- a/verification/base.py
+++ b/verification/base.py
@@ -28,13 +28,7 @@ class DiscardPending(Exception):
 
 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()
@@ -73,13 +67,7 @@ class Verified(model.PersistentMixIn):
 
 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()."""
@@ -92,13 +80,10 @@ class IVerifierStatus(model.PersistentMixIn):
 
 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