使用Demo的视频检测时，result文件夹下的输出视频只有两百多字节，且无法打开输出视频
Created by: Forestyuting
视频指定到了文件：python infer.py --models_dir=E:/detection/PaddleHub/demo/mask_detection/python/pyramidbox_lite_server_mask --video_path=E:/detection/PaddleHub/demo/mask_detection/python/videos/2.mp4
