巨坑慎入：
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/python-2.7.5-68.el7.x86_64.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/python-devel-2.7.5-68.el7.x86_64.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/python-libs-2.7.5-68.el7.x86_64.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/python-pycurl-7.19.0-19.el7.x86_64.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/python-setuptools-0.9.8-7.el7.noarch.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/python-urlgrabber-3.10-8.el7.noarch.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/iniparser-3.1-5.el7.x86_64.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/rpm-python-4.11.3-32.el7.x86_64.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/yum-3.4.3-158.el7.centos.noarch.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/yum-metadata-parser-1.1.4-10.el7.x86_64.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/yum-utils-1.1.31-45.el7.noarch.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.31-45.el7.noarch.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/yum-plugin-protectbase-1.1.31-45.el7.noarch.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/yum-plugin-aliases-1.1.31-45.el7.noarch.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/python-backports-ssl_match_hostname-3.5.0.1-1.el7.noarch.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/python-backports-1.0-8.el7.x86_64.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/python-ipaddress-1.0.16-2.el7.noarch.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/libxml2-python-2.9.1-6.el7_2.3.x86_64.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/python-kitchen-1.1.1-5.el7.noarch.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/python-chardet-2.2.1-1.el7_1.noarch.rpm
wget http://mirror.centos.org/centos/7/os/x86_64/Packages/python-iniparse-0.4-9.el7.noarch.rpm
rpm -Uvh --replacepkgs python*.rpm
rpm -Uvh --replacepkgs rpm-python*.rpm yum*.rpm
sudo vim /usr/bin/yum
把文件头部的#!/usr/bin/python改成#!/usr/bin/python2.7保存退出即可.
/usr/libexec/urlgrabber-ext-down看看，发下他也使用了/usr/bin/python，于是跟前面一样，改为2.7，完成。