Change validators to use the validator_context

Change InstanceKeys to take a namedtuple for context

util/config/validators/validate_ldap.py

@@ -11,8 +11,11 @@ class LDAPValidator(BaseValidator):
   name = "ldap"
 
   @classmethod
-  def validate(cls, config, user, user_password, app):
+  def validate(cls, validator_context):
     """ Validates the LDAP connection. """
+    config = validator_context.config
+    user = validator_context.user
+    user_password = validator_context.user_password
     if config.get('AUTHENTICATION_TYPE', 'Database') != 'LDAP':
       return