Another app is currently holding the yum lock; waiting for it to exit..

A common note:
When we start installing something using fedora yum repository, and we stop in the midway, then we often see the following message if we issue any command using yum:

Another app is currently holding the yum lock; waiting for it to exit..
How to break the lock?

Solution:
1) Be root: type su; give the password
2) Break the lock: sudo rm /var/run/yum.pid

You are done. Have fun with yum :)