Add test/py/tests/test_fit_verity.py covering: - mkimage writes correct dm-verity properties for matched and mismatched block sizes (4096/4096 and 4096/1024); - veritysetup verify re-checks the digest against the .itb's external data section; - mkimage rejects dm-verity images built without -E. All tests are skipped if veritysetup is not installed on the host. Signed-off-by: Daniel Golle <daniel@makrotopia.org> Reviewed-by: Simon Glass <sjg@chromium.org>