Move toward python 3/2 compatible metaclass

Change-Id: Ia7e07a7530e26c388c5da3e362510233b6a65aa6

taskflow/engines/action_engine/base_action.py

@@ -19,10 +19,11 @@
 
 import abc
 
+import six
 
-class Action(object):
+
+class Action(six.with_metaclass(abc.ABCMeta)):
     """Base action class"""
-    __metaclass__ = abc.ABCMeta
 
     @abc.abstractmethod
     def execute(self, engine):

taskflow/engines/base.py

@@ -19,9 +19,11 @@
 
 import abc
 
+import six
 
-class EngineBase(object):
-    __metaclass__ = abc.ABCMeta
+
+class EngineBase(six.with_metaclass(abc.ABCMeta)):
+    """Base for all engines implementations"""
 
     def __init__(self, flow, flow_detail, backend, conf):
         self._flow = flow

taskflow/flow.py

@@ -18,11 +18,13 @@
 
 import abc
 
+import six
+
 from taskflow.openstack.common import uuidutils
 from taskflow.utils import reflection
 
 
-class Flow(object):
+class Flow(six.with_metaclass(abc.ABCMeta)):
     """The base abstract class of all flow implementations.
 
     It provides a name and an identifier (uuid or other) to the flow so that
@@ -33,8 +35,6 @@ class Flow(object):
     - __len__
     """
 
-    __metaclass__ = abc.ABCMeta
-
     def __init__(self, name, uuid=None):
         self._name = str(name)
         if uuid:

taskflow/jobs/job.py

@@ -35,6 +35,7 @@ class Job(object):
     so that the contained flows ownership can be transferred to the secondary
     entity for resumption/continuation/reverting.
     """
+
     def __init__(self, name, uuid=None):
         if uuid:
             self._uuid = uuid

taskflow/jobs/jobboard.py

@@ -19,14 +19,15 @@
 
 import abc
 
+import six
 
-class JobBoard(object):
+
+class JobBoard(six.with_metaclass(abc.ABCMeta)):
     """A jobboard is an abstract representation of a place where jobs
     can be posted, reposted, claimed and transferred. There can be multiple
     implementations of this job board, depending on the desired semantics and
     capabilities of the underlying jobboard implementation.
     """
-    __metaclass__ = abc.ABCMeta
 
     def __init__(self, name):
         self._name = name

taskflow/listeners/base.py

@@ -21,6 +21,8 @@ from __future__ import absolute_import
 import abc
 import logging
 
+import six
+
 from taskflow import states
 from taskflow.utils import misc
 
@@ -31,15 +33,13 @@ LOG = logging.getLogger(__name__)
 FINISH_STATES = (states.FAILURE, states.SUCCESS)
 
 
-class LoggingBase(object):
+class LoggingBase(six.with_metaclass(abc.ABCMeta)):
     """This provides a simple listener that can be attached to an engine which
     can be derived from to log the received actions to some logging backend. It
     provides a useful context manager access to be able to register and
     unregister with a given engine automatically when a context is entered and
     when it is exited.
     """
-    __metaclass__ = abc.ABCMeta
-
     def __init__(self, engine,
                  listen_for=misc.TransitionNotifier.ANY):
         self._listen_for = listen_for

taskflow/persistence/backends/base.py

@@ -18,12 +18,12 @@
 
 import abc
 
+import six
 
-class Backend(object):
+
+class Backend(six.with_metaclass(abc.ABCMeta)):
     """Base class for persistence backends."""
 
-    __metaclass__ = abc.ABCMeta
-
     def __init__(self, conf):
         self._conf = conf
 
@@ -38,11 +38,9 @@ class Backend(object):
         pass
 
 
-class Connection(object):
+class Connection(six.with_metaclass(abc.ABCMeta)):
     """Base class for backend connections."""
 
-    __metaclass__ = abc.ABCMeta
-
     @abc.abstractproperty
     def backend(self):
         """Returns the backend this connection is associated with."""

taskflow/storage.py

@@ -19,12 +19,14 @@
 import contextlib
 import logging
 
+import six
+
 from taskflow import exceptions
 from taskflow.openstack.common import uuidutils
 from taskflow.persistence import logbook
 from taskflow import states
 from taskflow.utils import misc
-from taskflow.utils import threading_utils
+from taskflow.utils import threading_utils as tu
 
 LOG = logging.getLogger(__name__)
 STATES_WITH_RESULTS = (states.SUCCESS, states.REVERTING, states.FAILURE)
@@ -284,5 +286,5 @@ class Storage(object):
         return state
 
 
-class ThreadSafeStorage(Storage):
-    __metaclass__ = threading_utils.ThreadSafeMeta
+class ThreadSafeStorage(six.with_metaclass(tu.ThreadSafeMeta, Storage)):
+    pass

taskflow/task.py

@@ -98,12 +98,10 @@ def _build_arg_mapping(task_name, reqs, rebind_args, function, do_infer):
     return result
 
 
-class BaseTask(object):
+class BaseTask(six.with_metaclass(abc.ABCMeta)):
     """An abstraction that defines a potential piece of work that can be
     applied and can be reverted to undo the work as a single unit.
     """
-    __metaclass__ = abc.ABCMeta
-
     TASK_EVENTS = ('update_progress', )
 
     def __init__(self, name, provides=None):