Could not open/read file:///etc/pki/rpm-gpg/RPM-GPG-KEY-puias
GPG key retrieval failed: [Errno 14] Could not open/read file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL
采用：
[root@localhost zhao]# yum install libX11-devel --nogpg
即可。
Ubuntu下编译libxml2出错：http://www.linuxdiyf.com/linux/14652.html
Linux环境下C使用的xml解析库:libxml2：http://www.linuxdiyf.com/linux/10901.html