There was a problem importing one of the Python modules
required to run yum. The error leading to this problem was:
No module named yum
Please install a package which provides this module, or
verify that the module is installed correctly.
It's possible that the above module doesn't match the
current version of Python, which is:
2.7.10 (default, Nov 21 2016, 18:47:42)
[GCC 4.4.7 20120313 (Red Hat 4.4.7-4)]
If you cannot solve this problem yourself, please go to
the yum faq at:
http://yum.baseurl.org/wiki/Faq
自己在百度上找了很久，都是说是Python的问题，因为不久前安装lnmp一键安装失败，也不知道什么原因，yum失效！卸载yum相关的rpm包重新安装，也重新安装了在百度上的几个Python的相关rpm包。改过/usr/bin/yum里的#/usr/bin/python的版本，也不管用。
求帮助！
看上去是你系统环境缺省的python中的yum模块找不到了。自己下载一个python的yum包安装试试