pulp_installer requires the firewall python package to be installed
As documented in https://pulp.plan.io/issues/6725, the managed system must have the python package "firewall" installed.
1st of all, this is only true if
pulp_configure_firewall is set to "auto" (the default) or "firewalld".
2nd, if firewalld is installed and running, but the python module for it is not installed, then we should install the distro package that provides it (for the distro's default python interpreter) when the variable is set to "auto" or "firewalld".
For reference on this being the intended behaviour of an ansible role, consider how the ansible apt module will automatically install the python3-apt package (presumably via commands) if it is missing.
If firewalld is not installed and running, then "auto" should do nothing.