Sometimes a document will reference an image that FOP is unable to find. With FOP 2.0, it will print a SEVERE log and then continue processing the file, eventually exiting with a regular zero exit code.
Because there may be a significant amount of other logs, and because this FOP was invoked from a makefile that renders a bunch of documents, it's easy to miss the log about the missing image. And because FOP appears to not use a non-zero exit code, the make command will also not complain.
How can I make FOP scream louder on missing images (and perhaps also other errors)? It could complete processing the file, but crucially I would like it to exit with a non-zero exit code so that make will stop with an error message.