use python 3 compatible exception messages
use python 3 compatible exception messages

macarthur-lab/seqr,macarthur-lab/seqr,ssadedin/seqr,ssadedin/seqr,ssadedin/seqr,macarthur-lab/seqr,macarthur-lab/seqr,ssadedin/seqr,ssadedin/seqr,macarthur-lab/seqr