2to3: use python3 in shell scripts
2to3: use python3 in shell scripts

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