'Downloads the manifest.xml and all AMI parts for image_id to destdir'

@print_timing('Downloading    image')
def download_image_files(self, image_id, destdir):

    if (not os.path.isdir(destdir)):
        raise exception.BaseException(("destination    directory    '%s'    does    not    exist" % destdir))
    widgets = ['file:    ', progressbar.Percentage(), '    ', progressbar.Bar(marker=progressbar.RotatingMarker()), '    ', progressbar.ETA(), '    ', progressbar.FileTransferSpeed()]
    files = self.get_image_files(image_id)
    def _dl_progress_cb(trans, total):
        pbar.update(trans)
    log.info(('Downloading    image:    %s' % image_id))
    for file in files:
        widgets[0] = ('%s:' % file.name)
        pbar = progressbar.ProgressBar(widgets=widgets, maxval=file.size).start()
        file.get_contents_to_filename(os.path.join(destdir, file.name), cb=_dl_progress_cb)
        pbar.finish()
