Forklift error: "This method is deprecated, please use the stdlib validate_legacy function, with Stdlib::Compat::Bool. There is further documentation for validate_legacy function in the README"

Problem:

While running the Forklift “katello.yml” ansible playbook, I get an error during the “foreman_installer : Run installer” task. It seems like a deprication warning, but it fails the task and the installer exits. Full output of this task paste-binned here (http://termbin.com/mypy). I can post more logs if necessary. I’m just running the vanilla Forklift playbook against a freshly installed CentOS 7.5.1804. I asked in IRC, but was told it’s probably a bug in the module and that I should post here.

Foreman and Proxy versions:
Latest CentOS 7, latest Forklift from GitHub, as of today.

Foreman and Proxy plugin versions:
Just running the Katello installer playbook from the Forklift Github, using the command line from the wiki:

ansible-playbook -l localhost playbooks/katello.yml -e foreman_repositories_version=1.14 -e katello_repositories_version=3.3

per https://github.com/theforeman/forklift/blob/master/docs/production.md#byob

Other relevant data:
http://termbin.com/mypy

Foreman 1.14 / Katello 3.3 is EOL. They had these deprecation warnings but they’ve been fixed in current versions.