Installation 即使在安装flatpak之后也无法创建沙盒

在如上所述克隆pitivi之后，我安装了flatpak。现在运行命令：

sudo apt install gnome-software-plugin-flatpak

我得到这个信息：

gnome-software-plugin-flatpak is already the newest version (3.28.1-0ubuntu4.18.04.12).

You need to install flatpak-builder >= 0.10.0 to be able to use the '/home/snpd/github/pitivi-dev/pitivi/build/flatpak/pitivi-flatpak' script.

You can find some information about how to install it for your distribution at:
    * http://flatpak.org/

并运行以下命令：

cd pitivi-dev/pitivi && source bin/pitivi-env

我得到这个信息：

gnome-software-plugin-flatpak is already the newest version (3.28.1-0ubuntu4.18.04.12).

You need to install flatpak-builder >= 0.10.0 to be able to use the '/home/snpd/github/pitivi-dev/pitivi/build/flatpak/pitivi-flatpak' script.

You can find some information about how to install it for your distribution at:
    * http://flatpak.org/

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我不知道这里出了什么问题，任何帮助或建议都将不胜感激。谢谢。

您需要安装一个单独的

flatpak builder

软件包