'Check that migrations don\'t cause downtime.
Schema migrations can be done online, allowing for rolling upgrades.'

def migrate_up(self, version, with_data=False):

    if ((version >= self.first_version) and (version not in self.exceptions)):
        banned_ops = self.banned_ops
    else:
        banned_ops = None
    with BannedDBSchemaOperations(banned_ops, self.migrate_file):
        super(KeystoneMigrationsCheckers, self).migrate_up(version, with_data)
