How to validate consistency of angular-translate (or other) json i18n files with groovy-maven-plugin

verify-i18n-json.groovy

import groovy.json.JsonSlurper

log.info("Verifying JSON translation files ...")

def root = new File(sprintf('%s/src/main/resources/static/i18n/', project.basedir))

def slurper = new JsonSlurper()
def allKeys = [] as Set
def tables = [:]
root.listFiles().each {
    if (it.name.endsWith(".json")) {
        def table = slurper.parse(it)
        allKeys.addAll(table.keySet())
        tables[it] = table
    }
}

def problem = false
tables.each {
    def file = it.key
    def table = it.value
    def difference = allKeys - table.keySet()
    difference.each {
        log.error("File '{}' is missing key '{}'", file.name, it)
    }
    if (!difference.isEmpty())
        problem = true
}

if (problem)
    throw new RuntimeException("I18N files are not consistent!")