Pass exit code along with sphinx-build

[iSOLveIT]

By @printfinn

I was trying to fail a Github Action early if there are warning/errors from sphinx build, for example, some images are missing, then there should be some warnings raised by sphinx-build.

If a step exits with a number other than 0, for example: exit(2), a Github Action can capture the errors, and stop the work flow earlier, and that build won't be pushed to the production website.

If I use only sphinx-build in a Github Action yaml file, the Github Action does stop early with a error, this is the expected behavior:

But when I use sphinx-pdf-generate, I found that Github Action is not stopping even if there are errors generated from sphinx-build (called internally be sphinx-pdf-generate):

When I see an error, I know I have mistakes, so I can fix the code: