This Issue is a duplicate of #5257, which should be reopened as it seems to have been closed in error. I would comment on that Issue, but unfortunately the conversation has been "closed".

My use case: I run jekyll as part of my CI, I would like my web devs to know when Jekyll throws an error. Currently the CI job "succeeds" because jekyll returns exit code zero, so my devs see the green checkmark and do not realize there is an error (for example a syntax error in a CSS file). There should indeed be a flag one can pass to jekyll which causes it to return a nonzero exit code when it encounters a parsing error.