Option --fail-if-warnings has no effect for writer warnings when converting to PDF via LaTeX

[tarleb]

The following command returns with the expected error code 3

$ echo '![](does-not-exist.jpg)' | pandoc -t docx -o /dev/null --fail-if-warnings
[WARNING] Could not fetch resource 'does-not-exist.jpg': PandocResourceNotFound "does-not-exist.jpg"
Failing because there were warnings.
$ echo $?
3

However, when converting to PDF via LaTeX, pandoc will signal success despite producing warnings:

$ echo '![](does-not-exist.jpg)' | pandoc -o /tmp/delete-me.pdf --fail-if-warnings
[WARNING] Could not fetch resource 'does-not-exist.jpg': replacing image with description
$ echo $?
0

Behavior is as expected whenever warnings are created by the reader:

$ echo '\include{does-not-exist.tex}' | pandoc -f latex -o /tmp/delete-me.pdf --fail-if-warnings
[WARNING] Could not load include file 'does-not-exist.tex' at line 1 column 29
Failing because there were warnings.
$ echo $?
3

It stands to argue that all of the above commands should fail.