sources.forEach((item, exists) -> failIfAnyMissing(item, exists, "sources"));

        if (shaFiles.isEmpty() == false) {
            throw new GradleException("Unused sha files found: \n" + joinFilenames(shaFiles));
        }

    }

    // This is just a marker output folder to allow this task being up-to-date.
    // The check logic is exception driven so a failed tasks will not be defined