Nicer error detection
Nicer error detection

jonfoster/pyxb1,jonfoster/pyxb2,jonfoster/pyxb2,jonfoster/pyxb-upstream-mirror,jonfoster/pyxb-upstream-mirror,pabigot/pyxb,balanced/PyXB,CantemoInternal/pyxb,balanced/PyXB,jonfoster/pyxb1,jonfoster/pyxb-upstream-mirror,jonfoster/pyxb2,CantemoInternal/pyxb,CantemoInternal/pyxb,balanced/PyXB,pabigot/pyxb