Code review comment for lp://qastaging/~rsalveti/linaro-image-tools/check-argument-before-use-boot-files

For me I find easier to read "if not cls.vmlinuz or not kernel" instead of "if not (cls.initrd and initrd), that's why I coded it this way.

You can check with leb-origen and lt-panda, both contain a valid device tree file.