I\'ve got a serious problem on Xcode 8 on macOS Sierra. when I try to build my app, I get the following issue.
CodeSign /Users/me/Library/Developer/Xcode/Der
I encountered this error on macOS Sierra 10.12.3, Xcode 8.2. Fixing the DerivedData did not work for me.
After I deleted an expired Apple Worldwide Developer Relations Certificate Authority certificate in Keychain Access the error went away.