HTTP/1.1 416 Requested Range Not Satisfiable
Content-Length: 0
Accept-Ranges: bytes
Server: TornadoServer/4.0.2
Last-Modified: Fri, 23 Jan 2015 12:44:46 GMT
Content-Range: bytes */6564
Etag: “90c84ce870ac7b09426b8ac2b3e329db”
Date: Fri, 23 Jan 2015 13:35:34 GMT
Content-Type: text/plain
使用新的AssetsManagerEx ，下载多个文件，会有1到2个文件出现416错误