title: pyenv virtualenv activation not work when use full path
body: <p>I install <code>pyenv</code> on centos, and check if its working.</p>
  
  <pre><code># curl -L https://raw.githubusercontent.com/pyenv/pyenv-installer/master/bin/pyenv-installer | bash
    % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                   Dload  Upload   Total   Spent    Left  Speed
  104  2099  104  2099    0     0  14121      0 --:--:-- --:--:-- --:--:-- 18575
  Initialized empty Git repository in /root/.pyenv/.git/
  remote: Counting objects: 4531, done.
  remote: Compressing objects: 100% (1831/1831), done.
  remote: Total 4531 (delta 3252), reused 3506 (delta 2419), pack-reused 0
  Receiving objects: 100% (4531/4531), 1019.80 KiB, done.
  Resolving deltas: 100% (3252/3252), done.
  Initialized empty Git repository in /root/.pyenv/plugins/pyenv-doctor/.git/
  remote: Counting objects: 18, done.
  remote: Compressing objects: 100% (11/11), done.
  remote: Total 18 (delta 5), reused 14 (delta 4), pack-reused 0
  Unpacking objects: 100% (18/18), done.
  Initialized empty Git repository in /root/.pyenv/plugins/pyenv-installer/.git/
  remote: Counting objects: 22, done.
  remote: Compressing objects: 100% (19/19), done.
  remote: Total 22 (delta 4), reused 13 (delta 0), pack-reused 0
  Unpacking objects: 100% (22/22), done.
  Initialized empty Git repository in /root/.pyenv/plugins/pyenv-update/.git/
  remote: Counting objects: 7, done.
  remote: Compressing objects: 100% (5/5), done.
  remote: Total 7 (delta 1), reused 3 (delta 0), pack-reused 0
  Unpacking objects: 100% (7/7), done.
  Initialized empty Git repository in /root/.pyenv/plugins/pyenv-virtualenv/.git/
  remote: Counting objects: 478, done.
  remote: Compressing objects: 100% (309/309), done.
  remote: Total 478 (delta 313), reused 271 (delta 144), pack-reused 0
  Receiving objects: 100% (478/478), 259.55 KiB, done.
  Resolving deltas: 100% (313/313), done.
  Initialized empty Git repository in /root/.pyenv/plugins/pyenv-which-ext/.git/
  remote: Counting objects: 20, done.
  remote: Compressing objects: 100% (12/12), done.
  remote: Total 20 (delta 2), reused 14 (delta 1), pack-reused 0
  Unpacking objects: 100% (20/20), done.
  
  WARNING: seems you still have not added 'pyenv' to the load path.
  
  # Load pyenv automatically by adding
  # the following to ~/.bash_profile:
  
  export PATH="/root/.pyenv/bin:$PATH"
  eval "$(pyenv init -)"
  eval "$(pyenv virtualenv-init -)"
  [root@localhost ~]# export PATH="/root/.pyenv/bin:$PATH"
  [root@localhost ~]# eval "$(pyenv init -)"
  [root@localhost ~]# eval "$(pyenv virtualenv-init -)"
  [root@localhost ~]#
  [root@localhost ~]#
  [root@localhost ~]# pyenv
  pyenv 1.2.1
  Usage: pyenv &lt;command&gt; [&lt;args&gt;]
  
  Some useful pyenv commands are:
     commands    List all available pyenv commands
     local       Set or show the local application-specific Python version
     global      Set or show the global Python version
     shell       Set or show the shell-specific Python version
     install     Install a Python version using python-build
     uninstall   Uninstall a specific Python version
     rehash      Rehash pyenv shims (run this after installing executables)
     version     Show the current Python version and its origin
     versions    List all Python versions available to pyenv
     which       Display the full path to an executable
     whence      List all Python versions that contain the given executable
  
  See `pyenv help &lt;command&gt;' for information on a specific command.
  For full documentation, see: https://github.com/pyenv/pyenv#readme
  </code></pre>
  
  <p>Installed new version python.</p>
  
  <pre><code># pyenv install 2.7.13
  Downloading Python-2.7.13.tar.xz...
  -&gt; https://www.python.org/ftp/python/2.7.13/Python-2.7.13.tar.xz
  Installing Python-2.7.13...
  WARNING: The Python readline extension was not compiled. Missing the GNU readline lib?
  WARNING: The Python bz2 extension was not compiled. Missing the bzip2 lib?
  WARNING: The Python sqlite3 extension was not compiled. Missing the SQLite3 lib?
  Installed Python-2.7.13 to /root/.pyenv/versions/2.7.13
  </code></pre>
  
  <p>Create virtualenv.</p>
  
  <pre><code># pyenv virtualenv 2.7.13 myenv
  Collecting virtualenv
    Using cached virtualenv-15.1.0-py2.py3-none-any.whl
  Installing collected packages: virtualenv
  Successfully installed virtualenv-15.1.0
  New python executable in /root/.pyenv/versions/2.7.13/envs/myenv/bin/python2.7
  Also creating executable in /root/.pyenv/versions/2.7.13/envs/myenv/bin/python
  Installing setuptools, pip, wheel...done.
  Requirement already satisfied: setuptools in /root/.pyenv/versions/2.7.13/envs/myenv/lib/python2.7/site-packages
  Requirement already satisfied: pip in /root/.pyenv/versions/2.7.13/envs/myenv/lib/python2.7/site-packages
  </code></pre>
  
  <p>When activate <code>myenv</code> its working fine.</p>
  
  <pre><code># pyenv activate myenv
  pyenv-virtualenv: prompt changing will be removed from future release. configure `export PYENV_VIRTUALENV_DISABLE_PROMPT=1' to simulate the behavior.
  (myenv) [root@localhost ~]# source deactivate
  pyenv-virtualenv: deactivate 2.7.13/envs/myenv
  </code></pre>
  
  <p>When I use full path, then it gives error.</p>
  
  <pre><code>[root@localhost ~]# which pyenv
  /root/.pyenv/bin/pyenv
  [root@localhost ~]# /root/.pyenv/bin/pyenv activate myenv
  
  Failed to activate virtualenv.
  
  Perhaps pyenv-virtualenv has not been loaded into your shell properly.
  Please restart current shell and try again.
  </code></pre>
  
  <p>I can use <code>pyenv</code> for my testing, but when I have to use <code>pyenv</code> in <code>ansible</code>, I have to give full path as <code>/root/.pyenv/bin/pyenv</code>.</p>