Ensures that task.message is of type unicode

It is likely that a task script might store the message in a format
which is not 'Text', like a json message. To ensure that we save the
task message in the appropriate format, we should typecast it.

partially implements bp async-glance-workers

Change-Id: I4eaebb75357d448d4ea458cd7fe5e4ac96b33ace

glance/domain/__init__.py

@@ -19,6 +19,7 @@ import datetime
 import uuid
 
 from oslo.config import cfg
+import six
 
 from glance.common import exception
 import glance.openstack.common.log as logging
@@ -338,6 +339,17 @@ class Task(object):
     def status(self):
         return self._status
 
+    @property
+    def message(self):
+        return self._message
+
+    @message.setter
+    def message(self, message):
+        if message:
+            self._message = six.text_type(message)
+        else:
+            self._message = six.text_type('')
+
     def _validate_task_status_transition(self, cur_status, new_status):
             valid_transitions = {
                 'pending': ['processing', 'failure'],

glance/tests/functional/v2/test_tasks.py

@@ -99,6 +99,7 @@ class TestTasks(functional.FunctionalTest):
         checked_keys = set([u'created_at',
                             u'id',
                             u'input',
+                            u'message',
                             u'owner',
                             u'schema',
                             u'self',

glance/tests/unit/test_domain.py

@@ -317,7 +317,7 @@ class TestTaskFactory(test_utils.BaseTestCase):
         self.assertIsNone(task.expires_at)
         self.assertEqual(owner, task.owner)
         self.assertEqual(task_input, task.task_input)
-        self.assertIsNone(task.message)
+        self.assertEqual(task.message, u'')
         self.assertIsNone(task.result)
 
     def test_new_task_invalid_type(self):
@@ -424,7 +424,7 @@ class TestTask(test_utils.BaseTestCase):
         self.task.succeed('{"location": "file://home"}')
         self.assertEqual(self.task.status, 'success')
         self.assertEqual(self.task.result, '{"location": "file://home"}')
-        self.assertEqual(self.task.message, None)
+        self.assertEqual(self.task.message, u'')
         expected = (timeutils.utcnow() +
                     datetime.timedelta(hours=CONF.task.task_time_to_live))
         self.assertEqual(