The exit status code '1' says something went wrong:
stderr: "xvfb-run: error: Xvfb failed to start
"
stdout: ""
command: xvfb-run -- /usr/bin/wkhtmltopdf --lowquality --margin-bottom '10mm' --margin-top '10mm' --orientation 'portrait' --page-size 'a4' '/tmp/knp_snappy6811e8e6c57891.15523979.html' '/tmp/knp_snappy6811e8e6c57d59.12417787.pdf'.
