issue on ubuntu 18.04

[goer99]

Describe the bug

Thanks for the scripts. However, installation is terminated by the error blow:

  检测到的系统: ubuntu 18.04 (x86_64)
  
  选择安装方式:
  1) 极速安装
  2) 从源代码编译
  选择一个选项 (1-2): 2
  正在安装编译 FFmpeg 所需的依赖...
  Hit:1 http://mirrors.aliyun.com/ubuntu bionic InRelease
  Hit:2 http://mirrors.aliyun.com/ubuntu bionic-security InRelease
  Hit:3 http://mirrors.aliyun.com/ubuntu bionic-updates InRelease
  Hit:4 http://mirrors.aliyun.com/ubuntu bionic-proposed InRelease
  Hit:5 http://mirrors.aliyun.com/ubuntu bionic-backports InRelease
  Hit:6 http://cn.archive.ubuntu.com/ubuntu bionic InRelease
  Hit:7 http://cn.archive.ubuntu.com/ubuntu bionic-updates InRelease
  Get:8 https://download.docker.com/linux/ubuntu bionic InRelease [64.4 kB]
  Hit:9 http://cn.archive.ubuntu.com/ubuntu bionic-backports InRelease
  Hit:10 http://cn.archive.ubuntu.com/ubuntu bionic-security InRelease
  Fetched 64.4 kB in 5s (12.9 kB/s)
  Traceback (most recent call last):
    File "/usr/lib/cnf-update-db", line 8, in <module>
      from CommandNotFound.db.creator import DbCreator
  ModuleNotFoundError: No module named 'CommandNotFound'
  Reading package lists... Done
  E: Problem executing scripts APT::Update::Post-Invoke-Success 'if /usr/bin/test -w /var/lib/command-not-found/ -a -e /usr/lib/cnf-update-db; then /usr/lib/cnf-update-db > /dev/null; fi'
  E: Sub-process returned an error code
  
  遇到错误。正在退出...
  如果您认为这是一个错误，请报告给我们。

Desktop (please complete the following information):

• OS: ubuntu
• Version [18.04]
• Root [yes]

[ZL-Asica]

感谢反馈，抱歉一直没有回复。这个问题我可能这周晚些看一下。在 Ubuntu 下可以采取直接使用 apt install 的方式进行安装（如果以后想要编译安装也方便卸载）。

Thank you so much for this bug report. Sorry for the late reply. Added to my personal backlog already. ETA to be fixed in a week.