I'm trying to upgrade Liberty to Mitaka and having a problem to upgrading db. If anyone can advice me to workaround this error, I'm very appreciated.

I'm following procedure shown in this link: https://www.rdoproject.org/install/upgrading-rdo-2/ (RDO - Upgrading from Liberty to Mitaka)

Procedure is the followings:

1) yum install https://www.rdoproject.org/repos/rdo-release.rpm (https://www.rdoproject.org/repos/rdo-...)

2) yum upgrade mariadb mariadb-server

3) yum install python2-PyMySQL

4) http://docs.openstack.org/mitaka/install-guide-rdo/keystone-install.html (modify keystone.conf according to installation document of Mitaka)

5) openstack-db --service keystone --update ==> got the following error

Traceback (most recent call last):
  File "/usr/bin/keystone-manage", line 6, in <module>
    from keystone.cmd.manage import main
  File "/usr/lib/python2.7/site-packages/keystone/cmd/manage.py", line 31, in <module>
    from keystone.cmd import cli
  File "/usr/lib/python2.7/site-packages/keystone/cmd/cli.py", line 31, in <module>
    from keystone.common import sql
  File "/usr/lib/python2.7/site-packages/keystone/common/sql/__init__.py", line 15, in <module>
    from keystone.common.sql.core import *  # noqa
  File "/usr/lib/python2.7/site-packages/keystone/common/sql/core.py", line 24, in <module>
    from oslo_db import exception as db_exception
  File "/usr/lib/python2.7/site-packages/oslo_db/exception.py", line 143, in <module>
    class DBInvalidUnicodeParameter(Exception):
  File "/usr/lib/python2.7/site-packages/oslo_db/exception.py", line 151, in DBInvalidUnicodeParameter
    @debtcollector.removals.removed_property
AttributeError: 'module' object has no attribute 'removed_property'
Can't determine the existing sync level.
Please ensure the database is running and already initialised.

My locale is "en_US.UTF-8" and my controller node is running with CentOS-7.2. MariaDB is running and initialized when I installed Liberty.

Regards