Another app is currently holding the yum lock: How to release it?

When you give YUM command to install, update, clean or whatever you will get the error message "Another app is currently holding the yum lock". But won't release by itself. The full error message you see in terminal will be like:

Another app is currently holding the yum lock; waiting for it to exit...
  The other application is: PackageKit
    Memory :  36 M RSS (448 MB VSZ)
    Started: Thu Jan 29 23:11:16 2015 - 11:24 ago
    State  : Sleeping, pid: 2356

How to release YUM lock

To release the lock you need to kill the pid mentioned in that error message. In my case PID is 2356, so I will give below command.

kill -9 2356

Change the pid as what you get in the command.

kill -9 <pid>