E: GPG error: http://mirrors.oschina.net trusty-backports InRelease: Clearsigned file isn't valid, got 'NODATA' (does the network require authentication?)

E: GPG error: http://mirrors.oschina.net trusty-backports InRelease: Clearsigned file isn't valid, got 'NODATA' (does the network require authentication?)

更新源的时候出现了这个错误提示。

网上没找到答案，估计是源有问题，把这个出错的源删除了就可以了。

或者找个全新的源