improve import vcf error message (#4289)
improve import vcf error message (#4289)

addresses #4283
cseed/hail,hail-is/hail,hail-is/hail,cseed/hail,cseed/hail,cseed/hail,hail-is/hail,danking/hail,cseed/hail,hail-is/hail,danking/hail,hail-is/hail,danking/hail,hail-is/hail,cseed/hail,danking/hail,cseed/hail,danking/hail,danking/hail,hail-is/hail,hail-is/hail,cseed/hail,danking/hail,danking/hail