Maven + Eclipse = Error?

If you face the something like the following error,

Unbound classpath variable: ‘M2_REPO/bouncycastle/bcmail-jdk14/132/bcmail-jdk14-132.jar

Select the Eclipse Project folder from the Navigator window view
Right Click and get the Project Properties.
Select the tree item named “Java Build Path”
Push the button on the Right that says Add Variables.
Then Push the button that says Configure Variables.
Then push the New button
Add a new variable named M2_REPO and map it to the directory that contains the repository above.
Exit back to the “New Variable Classpath entry” dialog.
Select the M2_REPO variable and click extend
Select a jar file and exit.