By setting ansible_python_interpreter for these fictious hosts we avoid
Ansible trying and failing to connect to them in a attempt to populate
ansible_facts.discovered_interpreter_python. This speeds up these tests by
avoiding a timeout.
It is also a necessary pre-requisite for Ansible 10 (ansible-core 2.17). In
that release no hardcoded fallback is used, failure to determine a valid
Python interpreter is a fatal error.
refs #1074
Alex Willmer