The operation couldn’t be completed. Unable to log in with account ''. An unexpected failure occurre

errors：The operation couldn’t be completed. Unable to log in with account 'myappleid'. An unexpected failure occurred while logging in (Underlying error code 1100).

解决方法：

 I had to go to "Preferences" -> "Accounts", where it turned out my Apple ID had timed-out. After logging-in there, and then restarting Xcode, my profile was automatically "repaired", and all is now well.