It will only occur if everything is so irrevocably on fire that you need to debug a lot of code anyway, at which point the error message is useless.
Specifically, the branch is only reachable if the PID is not what was expected, or the location that the macro was supposed to longjmp to is not set, which would be fatal defects.
I'd hate to be the poor soul who encounters this error message and finds no information about it except the source code.