【linux环境】tornado执行self.finish报错bad file descriptor

[Mulany_guo]

接收文件完成后会finish返回给对方信息，如下
file_metas = self.request.files['file']
for meta in file_metas:
result_path = os.path.join(upload_path, \
'result' + os.path.splitext(meta['filename'])[1])
with open(result_path, 'wb') as up:
up.write(meta['body'])
if os.path.exists(result_path):
data = {"err_desc": "扫描报告上传成功"}
taskhelper.update_task(taskid, data)
self.finish(json.dumps(ret))
retFlag = True


finish时会报错：