Finds installer translations either for a specific langcode or all languages.
$langcode: (optional) The language code corresponding to the language for which we want to find translation files. If omitted, information on all available files will be returned.
An associative array of file information objects keyed by file URIs as returned by file_scan_directory().
function install_find_translation_files($langcode = NULL) {
$directory = variable_get('locale_translate_file_directory', conf_path() . '/files/translations');
$files = file_scan_directory($directory, '!drupal-\\d+\\.\\d+\\.' . (!empty($langcode) ? preg_quote($langcode, '!') : '[^\\.]+') . '\\.po$!', array(
'recurse' => FALSE,
));
return $files;
}