It's not appropriate to backport the python-heatclient change to a z-stream, since it may break some scripts that run in an environment where they are connected to a tty (for example, we encountered this problem with Ansible in the upstream TripleO CI).

With reference to the OSPd undercloud specifically (as opposed to Heat in general), a far more robust way to ensure that the overcloud is never deleted is to either disallow it entirely or give permissions only to a separate user in policy.json. Since this occurs on the server side it doesn't depend on everyone using the correct version of the client, and you can actually require elevated privileges rather than just an extra keystroke to delete the overcloud.

To avoid this usability issue, there is going to be documentation provided on restricting policies for OSP7.