public function createDummyFolder($folderName)
    {
        $this->createDummyUploadFolder();
        $uniqueFolderName = $this->getUniqueFileOrFolderPath($folderName);

        if (!GeneralUtility::mkdir($uniqueFolderName)) {
            throw new Exception('The folder ' . $uniqueFolderName . ' could not be created.', 1334439333);
        }

        $relativeUniqueFolderName = $this->getPathRelativeToUploadDirectory($uniqueFolderName);

        // Adds the created dummy folder to the top of $this->dummyFolders so
        // it gets deleted before previously created folders through
        // $this->cleanUpFolders(). This is needed for nested dummy folders.
        $this->dummyFolders = [$relativeUniqueFolderName => $relativeUniqueFolderName] + $this->dummyFolders;

        return $uniqueFolderName;
    }