(#3541) Document improved error message.
(#3541) Document improved error message.

zhangzhehust/htcondor,htcondor/htcondor,htcondor/htcondor,zhangzhehust/htcondor,zhangzhehust/htcondor,htcondor/htcondor,djw8605/htcondor,htcondor/htcondor,htcondor/htcondor,zhangzhehust/htcondor,zhangzhehust/htcondor,djw8605/htcondor,zhangzhehust/htcondor,htcondor/htcondor,zhangzhehust/htcondor,djw8605/htcondor,neurodebian/htcondor,neurodebian/htcondor,neurodebian/htcondor,djw8605/htcondor,neurodebian/htcondor,djw8605/htcondor,zhangzhehust/htcondor,djw8605/htcondor,djw8605/htcondor,neurodebian/htcondor,htcondor/htcondor,djw8605/htcondor,zhangzhehust/htcondor,neurodebian/htcondor,htcondor/htcondor,neurodebian/htcondor,neurodebian/htcondor,djw8605/htcondor,neurodebian/htcondor