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
Sometimes even if you fixed and/or had correct code-signing done, the problem might lurk in 3rd-party packages.
If you closely check out your build error, you might find the name of the 3rd-party libraries on the error message.
In this case, you must build your 3rd-party libraries again. For example in my case, update it via carthage update and now the build succeeded properly.