Downloads the QC report from the DNAnexus sequencing results project.
    
        Args: 
            download_dir: `str` - The local directory path to download the QC report to.
    
        Returns: 
            `str`. The filepath to the downloaded FASTQC reports folder.

def download_fastqc_reports(self,download_dir):
        """
        Downloads the QC report from the DNAnexus sequencing results project.
    
        Args: 
            download_dir: `str` - The local directory path to download the QC report to.
    
        Returns: 
            `str`. The filepath to the downloaded FASTQC reports folder.
        """
        if not os.path.isdir(download_dir):
            os.makedirs(download_dir)  
        msg = "the FASTQC reports to {download_dir}.".format(download_dir=download_dir)
        debug_logger.debug("Downloading " + msg)
        dxpy.download_folder(project=self.dx_project_id,destdir=download_dir,folder=self.DX_FASTQC_FOLDER,overwrite=True)
        success_logger.info("Downloaded " + msg)
        #rename the downloaded folder to ${download_dir}/FASTQC
        return download_dir