old_contents: # Copyright 2011 Nicira, Inc.
  # All Rights Reserved.
  #
  #    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.
  
  from sqlalchemy import *
  from migrate import *
  
  from nova import log as logging
  from nova import utils
  
  
  meta = MetaData()
  
  # Add priority column to networks table
  priority = Column('priority', Integer())
  
  networks = Table('networks', meta, autoload=True)
  
  def upgrade(migrate_engine):
      meta.bind = migrate_engine
  
      try:
          networks.create_column(priority)
      except Exception:
          logging.error(_("priority column not added to networks table"))
          raise
  
  
  def downgrade(migrate_engine):
      meta.bind = migrate_engine
      networks.drop_column(priority)
  
new_contents: # Copyright 2011 Nicira, Inc.
  # All Rights Reserved.
  #
  #    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.
  
  from sqlalchemy import *
  from migrate import *
  
  from nova import log as logging
  from nova import utils
  
  
  meta = MetaData()
  
  # Add priority column to networks table
  priority = Column('priority', Integer())
  
  
  def upgrade(migrate_engine):
      meta.bind = migrate_engine
  
      networks = Table('networks', meta, autoload=True)
      try:
          networks.create_column(priority)
      except Exception:
          logging.error(_("priority column not added to networks table"))
          raise
  
  
  def downgrade(migrate_engine):
      meta.bind = migrate_engine
  
      networks = Table('networks', meta, autoload=True)
      networks.drop_column(priority)
  
subject: move networks declarations within upgrade/downgrade methods