Even though there is a task putting pyenv bin directory into PATH, but the code it produces is executed only if pyenv is already in PATH (basically it is never executed):

    - if which pyenv > /dev/null; then
    - "    export PYENV_ROOT=\\\"$HOME/.pyenv\\\""
    - "    export PATH=\\\"$PYENV_ROOT/bin:$PATH\\\""
    - "    eval \\\"$(pyenv init -)\\\""
    - "fi # pyenv"

All tasks are executed under the same user. Some tasks (namely, apt) require root access, so the whole role should be executed with "sudo: yes". But in this case pyenv will be installed under root as well, and will go (by default) into /root/.pyenv. It can be overwritten by pyenv_root variable, but it would still be owned by root, which would prevent regular user from using it.

All operations with pyenv itself should be performed with explicit "sudo: no"

TASK [pyenv : Install versions] ************************************************
task path: /Users/yujunz/Develop/denv/roles/pyenv/tasks/main.yml:4
[DEPRECATION WARNING]: Using bare variables is deprecated. Update your playbooks so that the environment value uses the full variable syntax ('{{pyenv_versions}}').
This feature
will be removed in a future release. Deprecation warnings can be disabled by setting deprecation_warnings=False in ansible.cfg.

t would be great if we could automate pyenv init step to actually activate pyenv.

When trying this role, it fails to install the versions:

TASK: [dirn.pyenv | Install versions] ***************************************** 
failed: [c.example.com] => (item=2.7.9) => {"cmd": "pyenv install 2.7.9", "failed": true, "item": "2.7.9", "rc": 2}
msg: [Errno 2] No such file or directory
failed: [c.example.com] => (item=3.4.3) => {"cmd": "pyenv install 3.4.3", "failed": true, "item": "3.4.3", "rc": 2}
msg: [Errno 2] No such file or directory
failed: [c.example.com] => (item=pypy-2.5.0) => {"cmd": "pyenv install pypy-2.5.0", "failed": true, "item": "pypy-2.5.0", "rc": 2}
msg: [Errno 2] No such file or directory
failed: [c.example.com] => (item=pypy3-2.4.0) => {"cmd": "pyenv install pypy3-2.4.0", "failed": true, "item": "pypy3-2.4.0", "rc": 2}
msg: [Errno 2] No such file or directory

FATAL: all hosts have already failed -- aborting

The pyenv command is not available yet: the Add to run commands task comes
later, and even then, the pyenv_runcom would need to be sourced before.

statically included: /Users/yujunz/Develop/denv/roles/pyenv/tasks/osx/pyenv.yml
[DEPRECATION WARNING]: Specifying include variables at the top-level of the task is deprecated. Please see:
http://docs.ansible.com/ansible/playbooks_roles.html#task-include-files-
and-encouraging-reuse

for currently supported syntax regarding included files and variables.
This feature will be removed in a future release. Deprecation warnings can be disabled
by setting deprecation_warnings=False in ansible.cfg.