class_docstr: Test case of invalid towhee command
docstr: target: test command 'downloadS3' absolute path
  method: use downloadS3 to download files in S3 absolute path with bucket_name
  expected: get error message
code: def test_command_downloadS3_absolute_path(self):
      """
      target: test command 'downloadS3' absolute path
      method: use downloadS3 to download files in S3 absolute path with bucket_name
      expected: get error message
      """
      res = os.popen(
          "towhee downloadS3 -pl ./ -pb s3://pretrainedweights.towhee.io/test/test.pt"
      ).read()
      assert "not exist" in res
      return True
  
file_path: towhee/tests/testcases/test_command.py
imports: import os
  import sys
  import towhee
label_desc: Use image node_id 4 for calling the TestCommandInvalid obj's underlying member method code with example usage: obj.test_command_downloadS3_absolute_path() and returns: True