Remove six.add_metaclass

With python 3.x, classes can use the metaclass= logic
to not require usage of the six library.

Subsequent patches will replace other six usages.

Change-Id: I5f52283b520a3d4b5a7a112afa85d668f9ec4881

barbican/common/validators.py

@@ -86,8 +86,7 @@ def validate_stored_key_rsa_container(project_id, container_ref, req):
                                  ctxt)
 
 
-@six.add_metaclass(abc.ABCMeta)
-class ValidatorBase(object):
+class ValidatorBase(object, metaclass=abc.ABCMeta):
     """Base class for validators."""
 
     name = ''

barbican/plugin/castellan_secret_store.py

@@ -26,8 +26,7 @@ from barbican.plugin.interface import secret_store as ss
 LOG = log.getLogger(__name__)
 
 
-@six.add_metaclass(abc.ABCMeta)
-class CastellanSecretStore(ss.SecretStoreBase):
+class CastellanSecretStore(ss.SecretStoreBase, metaclass=abc.ABCMeta):
 
     KEY_ID = "key_id"
     ALG = "alg"

barbican/plugin/crypto/base.py

@@ -13,8 +13,6 @@
 
 import abc
 
-import six
-
 from barbican.common import exception
 from barbican import i18n as u
 
@@ -240,8 +238,7 @@ class EncryptDTO(object):
         self.unencrypted = unencrypted
 
 
-@six.add_metaclass(abc.ABCMeta)
-class CryptoPluginBase(object):
+class CryptoPluginBase(object, metaclass=abc.ABCMeta):
     """Base class for all Crypto plugins.
 
     Barbican requests operations by invoking the methods on an instance of the

barbican/plugin/interface/certificate_manager.py

@@ -25,7 +25,6 @@ import datetime
 
 from oslo_config import cfg
 from oslo_utils import encodeutils
-import six
 from stevedore import named
 
 from barbican.common import config
@@ -203,8 +202,7 @@ class CertificateStatusInvalidOperation(exception.BarbicanHTTPException):
         self.client_message = self.message
 
 
-@six.add_metaclass(abc.ABCMeta)
-class CertificateEventPluginBase(object):
+class CertificateEventPluginBase(object, metaclass=abc.ABCMeta):
     """Base class for certificate eventing plugins.
 
     This class is the base plugin contract for issuing certificate related
@@ -239,8 +237,7 @@ class CertificateEventPluginBase(object):
         raise NotImplementedError  # pragma: no cover
 
 
-@six.add_metaclass(abc.ABCMeta)
-class CertificatePluginBase(object):
+class CertificatePluginBase(object, metaclass=abc.ABCMeta):
     """Base class for certificate plugins.
 
     This class is the base plugin contract for certificates.

barbican/plugin/interface/secret_store.py

@@ -16,7 +16,6 @@
 import abc
 
 from oslo_config import cfg
-import six
 from stevedore import named
 
 from barbican.common import config
@@ -389,8 +388,7 @@ class AsymmetricKeyMetadataDTO(object):
         self.passphrase_meta = passphrase_meta
 
 
-@six.add_metaclass(abc.ABCMeta)
-class SecretStoreBase(object):
+class SecretStoreBase(object, metaclass=abc.ABCMeta):
 
     @abc.abstractmethod
     def get_plugin_name(self):

barbican/tasks/resources.py

@@ -18,8 +18,6 @@ Task resources for the Barbican API.
 """
 import abc
 
-import six
-
 from barbican import api
 from barbican.common import utils
 from barbican import i18n as u
@@ -33,8 +31,7 @@ from barbican.tasks import common
 LOG = utils.getLogger(__name__)
 
 
-@six.add_metaclass(abc.ABCMeta)
-class BaseTask(object):
+class BaseTask(object, metaclass=abc.ABCMeta):
     """Base asynchronous task."""
 
     @abc.abstractmethod