Remove true/false return from action.execute()

In watcher/applier/workflow_engine/default.py, we are checking the
return value of action.execute(). As the "TODO" above indicates it
(line 118), we should get rid of this and only flag an action as
failed if an exception was raised during its execute(). We will
need to update the related unit tests.

Change-Id: Ia8ff7abd9994c3504e733ccd1d629cafe9d4b839
Closes-Bug: #1548383

watcher/applier/workflow_engine/default.py

@@ -22,6 +22,7 @@ from taskflow import task
 
 from watcher._i18n import _LE, _LW, _LC
 from watcher.applier.workflow_engine import base
+from watcher.common import exception
 from watcher.objects import action as obj_action
 
 LOG = log.getLogger(__name__)
@@ -77,10 +78,9 @@ class DefaultWorkFlowEngine(base.BaseWorkFlowEngine):
 
             e = engines.load(flow)
             e.run()
-            return True
+
         except Exception as e:
-            LOG.exception(e)
-            return False
+            raise exception.WorkflowExecutionException(error=e)
 
 
 class TaskFlowActionContainer(task.Task):
@@ -121,14 +121,9 @@ class TaskFlowActionContainer(task.Task):
         try:
             LOG.debug("Running action %s", self.name)
 
-            # todo(jed) remove return (true or false) raise an Exception
-            result = self.action.execute()
-            if result is not True:
-                self.engine.notify(self._db_action,
-                                   obj_action.State.FAILED)
-            else:
-                self.engine.notify(self._db_action,
-                                   obj_action.State.SUCCEEDED)
+            self.action.execute()
+            self.engine.notify(self._db_action,
+                               obj_action.State.SUCCEEDED)
         except Exception as e:
             LOG.exception(e)
             LOG.error(_LE('The WorkFlow Engine has failed '