[xml/rdf views] handle case where the user hasn't read access to a relation (closes #1984598) The view shouldn't crash in such case. Also refactor xmlrelateditem view and its call on the way.

#! /bin/sh -e
#

if [ "$1" = remove -o "$1" = upgrade ]; then
  if which install-docs >/dev/null 2>&1; then
    install-docs -r cubicweb-doc
  fi
fi

#DEBHELPER#

exit 0