Before:

  # nmcli c modify eth666 tc.qdiscs root
  Error: failed to modify tc.qdiscs: '(null)' is not a valid kind The valid syntax is: '[root | parent <handle>] [handle <handle>] <qdisc>'.

After:

  # nmcli c modify eth666 tc.qdiscs root
  Error: failed to modify tc.qdiscs: kind is missing. The valid syntax is: '[root | parent <handle>] [handle <handle>] <kind>'.