message: nydus-test: add a helper to generate specific lenght string
diff: @@ -6,6 +6,8 @@ import os
  import signal
  from typing import Tuple
  import io
  +import string
  +import random
  try:
  import psutil
  @@ -623,3 +625,8 @@ def parse_stargz(stargz):
  def docker_image_repo(reference):
  return posixpath.basename(reference).split(":")[0]
  +
  +
  +def random_string(l=64):
  + res = "".join(random.choices(string.ascii_uppercase + string.digits, k=l))
  + return res
  