错误信息1：
There was a problem importing one of the Python modules
required to run yum. The error leading to this problem was:
No module named urlgrabber
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:
2.6.6 (r266:84292, Nov 22 2013, 12:16:22)
[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
解决办法：
进入这个网址：http://urlgrabber.baseurl.org/download/
通过wget命令下载 wget http://urlgrabber.baseurl.org/download/urlgrabber-3.10.tar.gz
解压并进入该目录下执行该命令：python setup.py install
错误信息2：
Loaded plugins: fastestmirror
Error: File contains no section headers.
file: file://///etc/yum.repos.d/CentOS-Debuginfo.repo, line: 1
'eme=CentOS-6 - Debuginfo
'
执行如下命令即可解决：
cd /etc/yum
cd yum.repos.d
mv CentOS-Debuginfo.repo CentOS-Debuginfo.repo.bak