message: Use the default format.
diff: @@ -100,7 +100,7 @@ def main():
  os.remove(dmg_path)
  process = subprocess.Popen(["/usr/bin/hdiutil", "create",
  "-srcfolder", temp_dir,
  - "-format", "UDBZ", "-volname", options.volname,
  + "-volname", options.volname,
  dmg_path])
  process.wait()
  