pytask-parallel does not call the pytask_execute_task_protocol hook
specification/entry-point because pytask_execute_task_setup and pytask_execute_task
need to be separated from pytask_execute_task_teardown. Thus, plugins that change this
hook specification may not interact well with the parallelization.
Two PRs for CPython try to re-enable setting custom reducers which should have been working but does not. Here are the references.