centos 6.5升级到7报错？

[root@test_dan upgrade]# yum install redhat-upgrade-tool preupgrade-assistant-contents
已加载插件：fastestmirror, refresh-packagekit, security
设置安装进程
Loading mirror speeds from cached hostfile
解决依赖关系
--> 执行事务检查
---> Package preupgrade-assistant-contents.noarch 0:0.5.14-1.el6.centos will be 安装
--> 处理依赖关系 preupgrade-assistant(x86-64) >= 1.0.2-14，它被软件包 preupgrade-assistant-contents-0.5.14-1.el6.centos.noarch 需要
---> Package redhat-upgrade-tool.noarch 1:0.7.22-3.el6.centos will be 安装
--> 执行事务检查
---> Package preupgrade-assistant.x86_64 0:1.0.2-36.0.1.el6.centos will be 安装
--> 处理依赖关系 pkgconfig(libxml-2.0)，它被软件包 preupgrade-assistant-1.0.2-36.0.1.el6.centos.x86_64 需要
--> 处理依赖关系 pkgconfig(libxslt)，它被软件包 preupgrade-assistant-1.0.2-36.0.1.el6.centos.x86_64 需要
--> 完成依赖关系计算
错误：Package: preupgrade-assistant-1.0.2-36.0.1.el6.centos.x86_64 (upg)

      Requires: pkgconfig(libxslt)

错误：Package: preupgrade-assistant-1.0.2-36.0.1.el6.centos.x86_64 (upg)

      Requires: pkgconfig(libxml-2.0)

You could try using --skip-broken to work around the problem
You could try running: rpm -Va --nofiles --nodigest
[root@test_dan upgrade]# yum list|grep -i preupgrade-
preupgrade-assistant.x86_64
preupgrade-assistant-contents.noarch
preupgrade-assistant-ui.x86_64
[root@test_dan upgrade]# rpm -aq|grep -i libxslt
libxslt-1.1.26-2.el6_3.1.x86_64
[root@test_dan upgrade]# rpm -aq|grep -i libxml
libxml2-2.7.6-14.el6.x86_64
libxml2-python-2.7.6-14.el6.x86_64

这是什么错误？？