Invalid placeholder (!c) in string

[Nicolas-Bouteille]

The following line generates a PHP error in watchdogs:
$context['message'] = t('Importing row !c', ['!c' => $context['results']['rows_imported']]);
User error : Invalid placeholder (!c) in string
Seems like !placeholder is not supported anymore in D8:
https://www.drupal.org/node/2575819
$context['message'] = t('Importing row @row', ['@row' => $context['results']['rows_imported']]);
seems to be working well