Disallow initializing attributes using DOM nodes
Disallow initializing attributes using DOM nodes

Quietly extracting the attribute value from the DOM node and assigning it is
just too weird, and PyXB never does anything like this itself.

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