Centos7.5自带为/usr/bin/python2.7，需升级到python3.6，安装非常简单，直接通过yum.
#centos7 python
yum install epel-release -y
yum install https://centos7.iuscommunity.org/ius-release.rpm -y
yum install python36u -y
yum install python36u-pip -y
#修改yum python引用为 /usr/bin/python2.7
#第一行/usr/bin/python改为/usr/bin/python2.7
vim /usr/bin/yum
vim /usr/libexec/urlgrabber-ext-down
到这边全部结束...