Remove six from db module

This is part of the steps to remove usage of six library, which is no
longer needed since python 2 support was removed.

Change-Id: I529759167f960714ebf93be7b89ee849040361b2

magnum/db/api.py

@@ -19,7 +19,6 @@ import abc
 
 from oslo_config import cfg
 from oslo_db import api as db_api
-import six
 
 from magnum.common import profiler
 
@@ -35,8 +34,7 @@ def get_instance():
 
 
 @profiler.trace_cls("db")
-@six.add_metaclass(abc.ABCMeta)
+class Connection(object, metaclass=abc.ABCMeta):
-class Connection(object):
     """Base class for storage system connections."""
 
     @abc.abstractmethod

magnum/db/sqlalchemy/api.py

@@ -13,7 +13,6 @@
 # under the License.
 
 """SQLAlchemy storage backend."""
-import six
 
 from oslo_db import exception as db_exc
 from oslo_db.sqlalchemy import session as db_session
@@ -440,7 +439,7 @@ class Connection(api.Connection):
                 # NOTE(flwang): We only allow to update ClusterTemplate to be
                 # public, hidden and rename
                 if (not self._is_publishing_cluster_template(values) and
-                        list(six.viewkeys(values)) != ["name"]):
+                        list(values.keys()) != ["name"]):
                     raise exception.ClusterTemplateReferenced(
                         clustertemplate=cluster_template_id)
 

magnum/db/sqlalchemy/models.py

@@ -15,10 +15,10 @@
 """
 SQLAlchemy models for container service
 """
+from urllib import parse as urlparse
 
 from oslo_db.sqlalchemy import models
 from oslo_serialization import jsonutils
-import six.moves.urllib.parse as urlparse
 from sqlalchemy import Boolean
 from sqlalchemy import Column
 from sqlalchemy import DateTime