Failed without error message: xvfb-run -a --server-args="-screen 0, 1024x768x24" /usr/bin/wkhtmltopdf --use-xserver --orientation 'portrait' --page-size 'A4' --margin-top '10' --margin-bottom '10' --margin-left '10' --margin-right '10' '/tmp/tmp_wkhtmlto_pdf_niVH7s.html' '/tmp/tmp_wkhtmlto_pdf_aKn9qz.pdf'