# Add ONE constraint to several bones?

So, I want to add a Limit Rotation constraint with "Limit Z" option checked for many bones at once. Now, I know about the "Copy Constraints" function, BUT in this case, the bones already have other constraints on them (with different targets) which I want to keep, and just Copying all constraints would overwrite these.

How can I add only one constraint to other bones without overwriting existing ones?

import bpy