或者.rename(src,dest)throws文件在python中没有错误

我尝试在sftp服务器中远程重命名文件。 这是我的密码;

 srv = pysftp.Connection(host=host, username=username, password=password, port=port, cnopts=connOption)
    # Get the directory and file listing
    data = srv.listdir()

    try:
        for infile in data:
            if infile == filename:
                infile_without_ext = os.path.splitext(infile)[0]
                extension = os.path.splitext(infile)[1]
                new_file_name = infile_without_ext + "_" + str(datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S"))
                new_file_name_with_ext = new_file_name + extension

                print infile   //<----printing the file
                print new_file_name_with_ext

                os.rename(infile,  new_file_name_with_ext)

当我打印时 infile 它打印文件。但当我尝试重新命名时,我会出错;

OSError: [Errno 2] No such file or directory

我的文件在根目录中。 我怎么解决这个问题?