message: pdf: ensure fail on error
diff: @@ -183,7 +183,7 @@ tmp/scenegraph.tex: filter-latex.py scenegraph.md tmp/links.md tmp/images_local_
  newmd5s=`md5sum $$auxf 2> /dev/null`;\
  until [[ $$md5s == $$newmd5s ]]; do \
  md5s=$$newmd5s;\
  - xelatex -output-directory=tmp $<;\
  + xelatex -halt-on-error -output-directory=tmp $< || exit 2;\
  newmd5s=`md5sum $$auxf`;\
  done
  cp tmp/$(basename $<).pdf $@
  