从2月14号开始，上传AppStore时可能会碰到这个问题：
Failed to locate or generate matching signing assets
Xcode attempted to locate or generate matching signing assets and failed to do so because of the following issues.
Missing iOS Distribution signing identity for ... Xcode can request one for you.
截图如下：
原因是Apple World Wide Developer Relations Certificate Authority的过期时间是2016年2月14。苹果的回答如下：
Thanks for bringing this to the attention of the community and apologies for the issues you’ve been having. This issue stems from having a copy of the expired WWDR Intermediate certificate in both your System and Login keychains. To resolve the issue, you should first download and install the newWWDR intermediate certificate (by double-clicking on the file). Next, in the Keychain Access application, select the System keychain. Make sure to select “Show Expired Certificates” in the View menu and then delete the expired version of the Apple Worldwide Developer Relations Certificate Authority Intermediate certificate (expired on February 14, 2016). Your certificates should now appear as valid in Keychain Access and be available to Xcode for submissions to the App Store.
简单的说就是颁发开发者证书的根证书过期了。如果这个时候你打开keychain看你的发布证书会是这样的：
就是这个Apple World Wide Developer Relations Certificate Authority过期了，所以这个颁发的证书都不能使用了。
现在来说下解决方案：
1.打开keychain（钥匙串），在登录和系统中找到过期的 Apple World Wide Developer Relation Certification Authority，然后删除它
注意在keychain显示菜单下，设置成显示过期证书
2.下载这个链接里的AppleWWDRCA.cer的证书到本地
3.记得要把系统钥匙串的设置权限打开
4.把AppleWWDRCA.cer安装到登录和系统中
设置成功后就可以了。查看下你的发布证书是否已经正常了。
