[schema] Make syntax compatible with print_function
yams seems to exec() us sometimes (instead of __import__()), and
yams.reader uses print_function nowadays.
#! /bin/sh -e#if [ "$1" = configure ]; then if which install-docs >/dev/null 2>&1; then install-docs -i /usr/share/doc-base/cubicweb-doc fifi#DEBHELPER#exit 0