需要 CentOS 7 ，用 root 執行：
cd /etc/yum.repos.d/
wget https://download.opensuse.org/repositories/systemsmanagement:Uyuni:Stable:CentOS7-Uyuni-Client-Tools/CentOS_7/systemsmanagement:Uyuni:Stable:CentOS7-Uyuni-Client-Tools.repo
yum install python-defusedxml