安装walle的时候python总是报错，分析是python版本问题，想把系统python换成python3，删除/usr/bin/python的软链接后，把python3给链接上了，还是不行，脑子一抽执行了rpm -qa|grep python2|xargs rpm -ev --allmatches --nodeps和rpm -qa|grep python-2|xargs rpm -ev --allmatches --nodeps，悲剧的发现yum不能用了……
cat /etc/redhat-release 查看当前系统版本CentOS Linux release 7.8.2003 (Core)
在网上找了份yum的依赖表
libxml2-python-2.9.1-6.el7_2.3.x86_64.rpm
python-2.7.5-68.el7.x86_64.rpm
python-backports-1.0-8.el7.x86_64.rpm
python-backports-ssl_match_hostname-3.5.0.1-1.el7.noarch.rpm
python-chardet-2.2.1-1.el7_1.noarch.rpm
python-devel-2.7.5-68.el7.x86_64.rpm
python-iniparse-0.4-9.el7.noarch.rpm
python-ipaddress-1.0.16-2.el7.noarch.rpm
python-kitchen-1.1.1-5.el7.noarch.rpm
python-libs-2.7.5-68.el7.x86_64.rpm
python-pycurl-7.19.0-19.el7.x86_64.rpm
python-setuptools-0.9.8-7.el7.noarch.rpm
python-urlgrabber-3.10-8.el7.noarch.rpm
python-virtualenv-15.1.0-2.el7.noarch.rpm
rpm-4.11.3-32.el7.x86_64.rpm
rpm-build-4.11.3-32.el7.x86_64.rpm
rpm-build-libs-4.11.3-32.el7.x86_64.rpm
rpm-libs-4.11.3-32.el7.x86_64.rpm
rpm-python-4.11.3-32.el7.x86_64.rpm
rpm-sign-4.11.3-32.el7.x86_64.rpm
yum-3.4.3-158.el7.centos.noarch.rpm
yum-metadata-parser-1.1.4-10.el7.x86_64.rpm
yum-plugin-aliases-1.1.31-45.el7.noarch.rpm
yum-plugin-fastestmirror-1.1.31-45.el7.noarch.rpm
yum-plugin-protectbase-1.1.31-45.el7.noarch.rpm
yum-utils-1.1.31-45.el7.noarch.rpm
使用rpm -qa | grep xxx命令找少了哪个，然后从http://mirrors.ustc.edu.cn/centos/7/os/x86_64/Packages/里一个一个下载
还好只是卸载了python相关的，最后下载了这些
libxml2-python-2.9.1-6.el7.5.x86_64.rpm
python-2.7.5-89.el7.x86_64.rpm
python-backports-ssl_match_hostname-3.5.0.1-1.el7.noarch.rpm
python-devel-2.7.5-89.el7.x86_64.rpm
python-virtualenv-15.1.0-4.el7_7.noarch.rpm
rpm-build-4.11.3-45.el7.x86_64.rpm
rpm-sign-4.11.3-45.el7.x86_64.rpm
yum-plugin-aliases-1.1.31-54.el7_8.noarch.rpm
yum-plugin-protectbase-1.1.31-54.el7_8.noarch.rpm
执行rpm -ivh *.rpm --nodeps --force强制安装依赖，问题解决