Automatically use appropriate Python version with Jedi.el

Question

Documentation says that it can be done by making some variables buffer local. But how to make it correctly?

Can somebody show me example how to configure this jedi.el behaviour correctly?

Now I have two virtualenv with installed jedi for python 2 and 3. When I change working virtualenv or python buffer, I'll check current python version and if it has changed i call this function

(defun cm:jedi-setup-server ()
  "Setup Jedi server, update and reload."
  (interactive)
  (if (not (equal python-environment-default-root-name (cm:jedi-environment-root-name)))
      (progn
        (custom-set-variables
         '(python-environment-default-root-name (cm:jedi-environment-root-name))
         '(jedi:server-command
           (concat (venv-name-to-dir (cm:jedi-environment-root-name)) "bin/jediepcserver")))
        (jedi:install-server-block))))