Remove six useage

We don't support python2 anymore so we don't need this compatibility
library.

This patch remove six useage.

Change-Id: I5802ee67960ff8c53bc33213cc5aa8baee0d0dce

freezer_dr/evacuators/common/driver.py

@@ -12,11 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import abc
-import six
 
 
-@six.add_metaclass(abc.ABCMeta)
-class EvacuatorBaseDriver(object):
+class EvacuatorBaseDriver(object, metaclass=abc.ABCMeta):
     """
     Abstract class for all evacuation drivers should implement to have
     a unified interface

freezer_dr/fencers/common/driver.py

@@ -15,11 +15,9 @@
 """Abstract fencer"""
 
 import abc
-import six
 
 
-@six.add_metaclass(abc.ABCMeta)
-class FencerBaseDriver(object):
+class FencerBaseDriver(object, metaclass=abc.ABCMeta):
 
     """Abstract class that all fencer plugins.
 

freezer_dr/monitors/common/driver.py

@@ -13,15 +13,13 @@
 # limitations under the License.
 
 import abc
-import six
 
 from oslo_config import cfg
 
 CONF = cfg.CONF
 
 
-@six.add_metaclass(abc.ABCMeta)
-class MonitorBaseDriver(object):
+class MonitorBaseDriver(object, metaclass=abc.ABCMeta):
     """
     Abstract class that all monitoring plugins should implement to have a
     unified interface and as many plugins as we want...

freezer_dr/notifiers/common/driver.py

@@ -12,11 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 import abc
-import six
 
 
-@six.add_metaclass(abc.ABCMeta)
-class NotifierBaseDriver(object):
+class NotifierBaseDriver(object, metaclass=abc.ABCMeta):
     """ Used to notify admins/users at any stage that an error happened or
     process completed or something went wrong !
     """

freezer_dr/notifiers/drivers/slack/slack.py

@@ -16,9 +16,8 @@ from freezer_dr.notifiers.common.driver import NotifierBaseDriver
 import json
 from oslo_log import log
 import requests
-from six.moves import urllib
 import time
-
+import urllib.parse
 
 LOG = log.getLogger(__name__)
 

lower-constraints.txt

@@ -105,7 +105,6 @@ rfc3986==1.1.0
 Routes==2.4.1
 setuptools==21.0.0
 simplejson==3.13.2
-six==1.10.0
 snowballstemmer==1.2.1
 Sphinx==1.6.2
 sphinxcontrib-websupport==1.0.1