Metaclass Python 3.x Compatibility

According to the OpenStack style guide (http://docs.openstack.org/developer/hacking/), for Python 3.x compatibility use "six.add_metaclass" instead of " __metaclass__."

Change-Id: Ic7733a22294ecad30d185851d4f550f1386581fc

barbican/common/validators.py

@@ -39,10 +39,10 @@ def get_invalid_property(validation_error):
         return validation_error.schema_path[1]
 
 
+@six.add_metaclass(abc.ABCMeta)
 class ValidatorBase(object):
     """Base class for validators."""
 
-    __metaclass__ = abc.ABCMeta
     name = ''
 
     @abc.abstractmethod

barbican/crypto/plugin.py

@@ -18,6 +18,7 @@ import abc
 from Crypto.Cipher import AES
 from Crypto import Random
 from oslo.config import cfg
+import six
 
 from barbican.openstack.common.gettextutils import _
 
@@ -121,11 +122,10 @@ def indicate_bind_completed(kek_meta_dto, kek_datum):
     kek_datum.plugin_meta = kek_meta_dto.plugin_meta
 
 
+@six.add_metaclass(abc.ABCMeta)
 class CryptoPluginBase(object):
     """Base class for Crypto plugins."""
 
-    __metaclass__ = abc.ABCMeta
-
     @abc.abstractmethod
     def encrypt(self, encrypt_dto, kek_meta_dto, keystone_id):
         """Encrypt unencrypted data in the context of the provided tenant.

barbican/tasks/resources.py

@@ -18,6 +18,8 @@ Task resources for the Barbican API.
 """
 import abc
 
+import six
+
 from barbican import api
 from barbican.common import resources as res
 from barbican.common import utils
@@ -29,11 +31,10 @@ from barbican.openstack.common import gettextutils as u
 LOG = utils.getLogger(__name__)
 
 
+@six.add_metaclass(abc.ABCMeta)
 class BaseTask(object):
     """Base asychronous task."""
 
-    __metaclass__ = abc.ABCMeta
-
     @abc.abstractmethod
     def get_name(self):
         """A hook method to return a short localized name for this task.