wkhtmltopdf has very different behavior when certain resources fail to load, which depends on the URL of the resource.
Simply changing the URL of the failed resource changes the exit code of wkhtmltopdf. Certain URLs cause a ContentNotFoundError with an exit code of 1, and others are ignored with an exit code of 0.
All of these tests seem like they should have at least the same exit code.
Tested with wkhtmltopdf 0.12.2.1 (with patched qt).
wkhtmltopdf test1.html test1.pdf