    def test_command_downloadS3_nonexistent_path(self):
        """
        target: test command 'downloadS3' nonexistent path
        method: use downloadS3 to download files with nonexistent path
        expected: get error message
        """
        res = os.popen("towhee downloadS3 -pl ./ -pb bac/lpl.pt").read()
        assert "not exist" in res
        return True
target: test command 'downloadS3' nonexistent path
method: use downloadS3 to download files with nonexistent path
expected: get error message
tests/testcases/test_command.py