linux Python升级导致Yum无法使用

 yum -y install libtool 
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:
2.7.8 (default, Apr  7 2017, 03:20:15) 
[GCC 4.4.7 20120313 (Red Hat 4.4.7-17)]


If you cannot solve this problem yourself, please go to 
the yum faq at:
  http://yum.baseurl.org/wiki/Faq


错误原因：错误信息描述为 yum 所依赖的python 不相符，提示当前版本是2.7.8可能版本不匹配。没有yum依赖的包。
3、查看yum版本
rpm -qa |grep yum
4、查看python版本
 whereis python
python: /usr/bin/python2.4 /usr/bin/python /usr/lib/python2.4 /usr/local/bin/python2.6 /usr/local/bin/python2.6-config /usr/local/bin/python /usr/local/lib/python2.6 /usr/share/man/man1/python.1.gz
果然装了两个版本python
5、执行python，查看到使用2.6.1的版本
Python 2.7.8 (default, Apr  7 2017, 03:20:15) 
[GCC 4.4.7 20120313 (Red Hat 4.4.7-17)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
6、猜测yum调用了高版本的python。
7、解决方法：
查找yum文件,并编辑此py文件
 which yum
/usr/bin/yum
vi /usr/bin/yum
将
#!/usr/bin/python
改为:
#!/usr/bin/python2.6


然后保存OK.
yum -y install libtool 


补充：yum基于python写的。