ansible.tags = ENV['ANSIBLE_TAGS']

Here's an issue that you may figure should be addressed by the user, not by Trellis.

I use pyenv to manage python versions on my machine. Even after uninstalling Ansible, a shim remains at /usr/local/var/pyenv/shims/ansible-playbook, causing an incorrect return value from this which(cmd).

Here's a potential change that resolves it on my machine (dev/null handling from here):

- return exe if File.executable?(exe) && !File.directory?(exe)
+ return system("#{exe} --help", [:out, :err] => File::NULL) if File.executable?(exe) && !File.directory?(exe)

This appeals to me because it tests whether the ansible-playbook command actually works rather than just whether it should work, the latter being assumed based on the presence of the exe. I don't know whether this revised approach would be good practice or acceptable ruby.

It the change above is applied, it returns true, false, or nil, if I recall correctly (instead of exe path). So, maybe the name which() should change to something like cmd_valid(cmd).