Change validators to use the validator_context

Change InstanceKeys to take a namedtuple for context

util/config/validators/validate_signer.py

@@ -8,8 +8,10 @@ class SignerValidator(BaseValidator):
   name = "signer"
 
   @classmethod
-  def validate(cls, config, user, user_password, app):
+  def validate(cls, validator_context):
     """ Validates the GPG public+private key pair used for signing converted ACIs. """
+    config = validator_context.config
+
     if config.get('SIGNING_ENGINE') is None:
       return