DEPR: iterkv change Deprecation to FutureWarning
So this is visible to the users (already long time deprecated in the docs)

what exactly is the difference between a `Deprecation` and `Future` warning?
 DeprecationWarning is not visible to users (by default), FutureWarning is

That is the reason we use mostly FutureWarnings
 oh ok, good to know.
 Problem is that you actually want a combination of both: only show the warning if you call the function/method triggering it, and not when a library that you are using calls such a method. But AFAIK that is not possible.
