Defines a child class of Drupal\Core\Updater\UpdaterException that indicates a Drupal\Core\FileTransfer\FileTransferInterface exception.
We have to catch Drupal\Core\FileTransfer\FileTransferInterface exceptions and wrap those in t(), since Drupal\Core\FileTransfer\FileTransferInterface is so low-level that it doesn't use any Drupal APIs and none of the strings are translated.
Expanded class hierarchy of UpdaterFileTransferException
class UpdaterFileTransferException extends UpdaterException {
}