[root@CentOS ~]# yum list

There was a problem importing one of the Python modules

required to run yum. The error leading to this problem was:

   /usr/lib/python2.6/site-packages/pycurl.so: undefined symbol: CRYPTO_set_locking_callback

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, Jul 23 2015, 14:41:34) 

[GCC 4.4.7 20120313 (Red Hat 4.4.7-11)]

If you cannot solve this problem yourself, please go to 

the yum faq at:

  http://yum.baseurl.org/wiki/Faq

什么原因？怎么解决？