Reading through https://github.com/checkstyle/checkstyle/blob/489ce031e818f955a95c10d9f10668cb1b7b4b54/src/main/java/com/puppycrawl/tools/checkstyle/api/LocalizedMessage.java#L367-L377 showed that we actually need to pass in the Locale for the given bundle, to load the correct message. The Locale we should load is the Locale.getDefault().