feat(storage): do not restrict the container type

In Python, container is a concept, not a specific type.  The original
implementation limit the container to list, while this change allow you
to use other containers, like tuple, to supply as a sequence of the
message IDs.

Change-Id: I347e764ed0e965f17aa49f3e80f2f100ba8ba495

marconi/storage/base.py

@@ -188,8 +188,8 @@ class MessageBase(ControllerBase):
         :param queue: Name of the queue to get the
             message from.
         :param project: Project id
-        :param message_ids: One or more message IDs. Can be a single
-            string ID or a list of IDs.
+        :param message_ids: One message ID or a
+            sequence of message IDs.
 
         :returns: An iterable, yielding dicts containing message details
         :raises: DoesNotExist

marconi/storage/mongodb/messages.py

@@ -26,6 +26,7 @@ import datetime
 import time
 
 import pymongo.errors
+import six
 
 import marconi.openstack.common.log as logging
 from marconi.openstack.common import timeutils
@@ -367,7 +368,7 @@ class MessageController(storage.MessageBase):
 
     @utils.raises_conn_error
     def get(self, queue, message_ids, project=None):
-        if not isinstance(message_ids, list):
+        if isinstance(message_ids, six.string_types):
             message_ids = [message_ids]
 
         message_ids = [utils.to_oid(id) for id in message_ids]

marconi/storage/sqlite/messages.py

@@ -14,6 +14,8 @@
 # limitations under the License.
 
 
+import six
+
 from marconi.storage import base
 from marconi.storage import exceptions
 from marconi.storage.sqlite import utils
@@ -41,7 +43,7 @@ class MessageController(base.MessageBase):
         if project is None:
             project = ''
 
-        if not isinstance(message_ids, list):
+        if isinstance(message_ids, six.string_types):
             message_ids = [message_ids]
 
         message_ids = ["'%s'" % utils.msgid_decode(id) for id in message_ids]