'Update the expiring objects container when objects are updated.
:param op: operation performed (ex: \'PUT\', or \'DELETE\')
:param delete_at: scheduled delete in UNIX seconds, int
:param account: account name for the object
:param container: container name for the object
:param obj: object name
:param request: the original request driving the update
:param objdevice: device name that the object is in
:param policy: the BaseStoragePolicy instance (used for tmp dir)'

def delete_at_update(self, op, delete_at, account, container, obj, request, objdevice, policy):

    if config_true_value(request.headers.get('x-backend-replication', 'f')):
        return
    delete_at = normalize_delete_at_timestamp(delete_at)
    updates = [(None, None)]
    partition = None
    hosts = contdevices = [None]
    headers_in = request.headers
    headers_out = HeaderKeyDict({'X-Backend-Storage-Policy-Index': 0, 'x-timestamp': request.timestamp.internal, 'x-trans-id': headers_in.get('x-trans-id', '-'), 'referer': request.as_referer()})
    if (op != 'DELETE'):
        delete_at_container = headers_in.get('X-Delete-At-Container', None)
        if (not delete_at_container):
            self.logger.warning(('X-Delete-At-Container    header    must    be    specified    for    expiring    objects    background    %s    to    work    properly.    Making    best    guess    as    to    the    container    name    for    now.' % op))
            delete_at_container = get_expirer_container(delete_at, self.expiring_objects_container_divisor, account, container, obj)
        partition = headers_in.get('X-Delete-At-Partition', None)
        hosts = headers_in.get('X-Delete-At-Host', '')
        contdevices = headers_in.get('X-Delete-At-Device', '')
        updates = [upd for upd in zip((h.strip() for h in hosts.split(',')), (c.strip() for c in contdevices.split(','))) if (all(upd) and partition)]
        if (not updates):
            updates = [(None, None)]
        headers_out['x-size'] = '0'
        headers_out['x-content-type'] = 'text/plain'
        headers_out['x-etag'] = 'd41d8cd98f00b204e9800998ecf8427e'
    else:
        delete_at_container = get_expirer_container(delete_at, self.expiring_objects_container_divisor, account, container, obj)
    delete_at_container = normalize_delete_at_timestamp(delete_at_container)
    for (host, contdevice) in updates:
        self.async_update(op, self.expiring_objects_account, delete_at_container, ('%s-%s/%s/%s' % (delete_at, account, container, obj)), host, partition, contdevice, headers_out, objdevice, policy)
