渲染时捕获IOError：“无此文件或目录”尝试查看图像时出错

    def _get_thumb_url(self, folder, size):
        \"\"\" get a thumbnail giver a folder and a size. \"\"\"
        if not self.coverart:
            return \'#\'
        upload_to = path.dirname(self.coverart.path)
        tiny = path.join(upload_to, folder, path.basename(self.coverart.path))
        tiny = path.normpath(tiny)
        if not path.exists(tiny):
            import Image
            im = Image.open(self.coverart.path)
            im.thumbnail(size, Image.ANTIALIAS)
            im.save(tiny, \'JPEG\')
        return path.join(path.dirname(self.coverart.url), folder, path.basename(self.coverart.path))

    def get_thumb_url(self):
        return self._get_thumb_url(\'thumb_100_100\', (100,100))

    def thumb(self):
        \"\"\" Get thumb <a>. \"\"\"
        link = self.get_thumb_url()
        if link is None:
            return \'<a href=\"#\" target=\"_blank\">NO IMAGE</a>\'
        else:
            return \'<img src=%s />\' % (link)
    thumb.allow_tags = True

    def fullpicture(self):
        \"\"\" Get full picture <a>. \"\"\"
        link = \"%s%s\" % (settings.MEDIA_URL, self.coverart)
        if link is None:
            return \'<a href=\"#\" target=\"_blank\">NO IMAGE</a>\'
        else:
            return \'<img src=%s />\' % (link)
    thumb.allow_tags = True

<div class=\"coverart\" >{{ spmodel.thumb|safe }}</div>

<div class=\"coverart\" >{{ sp.fullpicture|safe }}</div>