message: macOS deploy: use the new plistlib API
  See
  The new API was added in 3.4 and old removed in 3.9.
  Github-Pull: 20298
  Rebased-From:
diff: @@ -586,7 +586,8 @@ if len(config.fancy) == 1:
  sys.exit(1)
  try:
  - fancy = plistlib.readPlist(p)
  + with open(p, 'rb') as fp:
  + fancy = plistlib.load(fp, fmt=plistlib.FMT_XML)
  except:
  if verbose >= 1:
  sys.stderr.write("Error: Could not parse fancy disk image plist at \"{}\"\n".format(p))
  