Error: File /var/cache/yum/x86_64/6/epel/metalink.xml is not XML

$ sudo yum update
Loaded plugins: fastestmirror, security
Setting up Update Process
Loading mirror speeds from cached hostfile
Error: File /var/cache/yum/x86_64/6/epel/metalink.xml is not XML

「Error: File /var/cache/yum/x86_64/6/epel/metalink.xml is not XML」というエラーが出る場合以下を実行する。

$ sudo yum clean all