public function getAssetDirectory()
{
$mergedFileDirectory = StaticContainer::get('path.tmp') . '/assets';
if (!is_dir($mergedFileDirectory)) {
Filesystem::mkdir($mergedFileDirectory);
}
if (!is_writable($mergedFileDirectory)) {
throw new Exception("Directory " . $mergedFileDirectory . " has to be writable.");
}
return $mergedFileDirectory;
}