my friends were talking about especially bad error messages to spring on a user so I'm reboggling this absolute gem
tbf I'm probably one of the only people in the world to ever get this error, because it involved the extreme edge case of forgetting to finalize a pending OS upgrade and closing the laptop's lid for a month, and the OS doesn't want to install update files that were signed ages ago so that known-buggy updates can't stay in circulation forever; what it SHOULD have said is "The downloaded update files have expired. They will need to be downloaded again."