code: public static function handleRunOnce()
  	{
  		try
  		{
  			$files = System::getContainer()->get('contao.resource_locator')->locate('config/runonce.php', null, false);
  		}
  		catch (\InvalidArgumentException $e)
  		{
  			return;
  		}
  
  		foreach ($files as $file)
  		{
  			try
  			{
  				include $file;
  			}
  			catch (\Exception $e) {}
  
  			$strRelpath = StringUtil::stripRootDir($file);
  
  			if (!unlink($file))
  			{
  				throw new \Exception("The file $strRelpath cannot be deleted. Please remove the file manually and correct the file permission settings on your server.");
  			}
  
  			System::log("File $strRelpath ran once and has then been removed successfully", __METHOD__, TL_GENERAL);
  		}
  	}
docs: Handle "runonce" files
  
  @throws \Exception