用Xcode 6.3.2 制作静态库时，总是提示
No valid signing identities (i.e. certificate and private key pair) matching the team ID “(null)” were found.
Xcode can attempt to fix this issue.
导致制作失败。上网查的找到的原因也看不懂，跪求大神指导。
下面是网址找到原因的网址：http://stackoverflow.com/questions/25901269/xcode-attempted-to-locate-or-generate-matching-signing-assets-and-failed-to-do-s
No valid signing identities (i.e. certificate and private key pair) matching the team ID “(null)” were found.
Xcode can attempt to fix this issue.
导致制作失败。上网查的找到的原因也看不懂，跪求大神指导。
下面是网址找到原因的网址：http://stackoverflow.com/questions/25901269/xcode-attempted-to-locate-or-generate-matching-signing-assets-and-failed-to-do-s
Code Sign error: No code signing identities found: No valid signing identities (i.e. certificate and private key pair) matching the team ID “(null)” were found.
CodeSign error: code signing is required for product type 'Unit Test Bundle' in SDK 'iOS 8.3'你看这是怎么回事，我用低版本的Xcode就没有这问题，什么情况啊？