linux环境下，遇见此错误，说明你已经下载了，并处于yum安装文件夹中，正在执行：[sudo] ./yummain.py install yum

• python-pycurl
  ::(此为python模块，如果你是python开发者，可通过pip pycurl安装，否则，rpm或者源码安装)

• python-urlgrabber
  ::(此为python模块，如果你是python开发者，可通过pip urlgrabber安装，否则，rpm或者源码安装)

• yum-metadata-parser
  ::(下载地址：，解压，进入解压后的目录，执行python setup.py install，然后再次执行：[sudo] ./yummain.py install yum)

如果安装成功之后，执行yum，报一下错误：

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:

2.7.12 (default,Nov  1 2016,15:50:51)

[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

解决：

 vim /usr/bin/yum; 
 然后将#!/usr/bin/python中的python解释器修改为低版本。