'Make the RPC call to export a volume backup.
Call backup manager to execute backup export.
:param context: running context
:param backup_id: backup id to export
:returns: dictionary -- a description of how to import the backup
:returns: contains \'backup_url\' and \'backup_service\'
:raises InvalidBackup:'

def export_record(self, context, backup_id):

    check_policy(context, 'backup-export')
    backup = self.get(context, backup_id)
    if (backup['status'] != fields.BackupStatus.AVAILABLE):
        msg = (_('Backup    status    must    be    available    and    not    %s.') % backup['status'])
        raise exception.InvalidBackup(reason=msg)
    LOG.debug('Calling    RPCAPI    with    context:    %(ctx)s,    host:    %(host)s,    backup:    %(id)s.', {'ctx': context, 'host': backup['host'], 'id': backup['id']})
    backup.host = self._get_available_backup_service_host(backup.host, backup.availability_zone)
    backup.save()
    export_data = self.backup_rpcapi.export_record(context, backup)
    return export_data
