old_contents: # Copyright 2010 United States Government as represented by the
  # Administrator of the National Aeronautics and Space Administration.
  # All Rights Reserved.
  #
  # Copyright 2013 OpenStack Foundation
  # Copyright 2013 IBM Corp.
  #
  #    Licensed under the Apache License, Version 2.0 (the "License"); you may
  #    not use this file except in compliance with the License. You may obtain
  #    a copy of the License at
  #
  #         http://www.apache.org/licenses/LICENSE-2.0
  #
  #    Unless required by applicable law or agreed to in writing, software
  #    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  #    License for the specific language governing permissions and limitations
  #    under the License.
  
  """Database setup and migration commands."""
  
  import os
  import threading
  
  from oslo_config import cfg
  from oslo_db import options as db_options
  from stevedore import driver
  
  
  _IMPL = None
  _LOCK = threading.Lock()
  
  db_options.set_defaults(cfg.CONF)
  
  
  def get_backend():
      global _IMPL
      if _IMPL is None:
          with _LOCK:
              if _IMPL is None:
                  _IMPL = driver.DriverManager(
                      "glance.database.migration_backend",
                      cfg.CONF.database.backend).driver
      return _IMPL
  
  
  # Migration-related constants
  EXPAND_BRANCH = 'expand'
  CONTRACT_BRANCH = 'contract'
  CURRENT_RELEASE = 'wallaby'
  ALEMBIC_INIT_VERSION = 'liberty'
  LATEST_REVISION = 'wallaby_contract01'
  INIT_VERSION = 0
  
  MIGRATE_REPO_PATH = os.path.join(
      os.path.abspath(os.path.dirname(__file__)),
      'sqlalchemy',
      'migrate_repo',
  )
  
new_contents: # Copyright 2010 United States Government as represented by the
  # Administrator of the National Aeronautics and Space Administration.
  # All Rights Reserved.
  #
  # Copyright 2013 OpenStack Foundation
  # Copyright 2013 IBM Corp.
  #
  #    Licensed under the Apache License, Version 2.0 (the "License"); you may
  #    not use this file except in compliance with the License. You may obtain
  #    a copy of the License at
  #
  #         http://www.apache.org/licenses/LICENSE-2.0
  #
  #    Unless required by applicable law or agreed to in writing, software
  #    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  #    License for the specific language governing permissions and limitations
  #    under the License.
  
  """Database setup and migration commands."""
  
  import os
  import threading
  
  from oslo_config import cfg
  from oslo_db import options as db_options
  from stevedore import driver
  
  
  _IMPL = None
  _LOCK = threading.Lock()
  
  db_options.set_defaults(cfg.CONF)
  
  
  def get_backend():
      global _IMPL
      if _IMPL is None:
          with _LOCK:
              if _IMPL is None:
                  _IMPL = driver.DriverManager(
                      "glance.database.migration_backend",
                      cfg.CONF.database.backend).driver
      return _IMPL
  
  
  # Migration-related constants
  EXPAND_BRANCH = 'expand'
  CONTRACT_BRANCH = 'contract'
  CURRENT_RELEASE = 'xena'
  ALEMBIC_INIT_VERSION = 'liberty'
  LATEST_REVISION = 'wallaby_contract01'
  INIT_VERSION = 0
  
  MIGRATE_REPO_PATH = os.path.join(
      os.path.abspath(os.path.dirname(__file__)),
      'sqlalchemy',
      'migrate_repo',
  )
  
subject: Change database migration version to xena