title: cannot load Python 3.5 interpreter for virtualenv
body: <p>I have installed Python 3.5 through Anaconda on the OSX system. After installing and activating the virtual environment, </p>
  
  <pre><code>virtualenv venv
  source venv/bin/activate
  </code></pre>
  
  <p>The Python version is Python 2.7.10. And while we are allowed to load the interpreter of our choice in <a href="http://docs.python-guide.org/en/latest/dev/virtualenvs/" rel="nofollow">virtualenv</a>, "/usr/bin/" only has folders for Python 2.6 and 2.7. After finding out the Anaconda python 3.5 path (   /Users/Username/anaconda/lib/python3.5)
  and trying to load it,</p>
  
  <blockquote>
    <p>for: virtualenv -p /Users/Username/anaconda/lib/python3.5 venv</p>
  </blockquote>
  
  <p>the code returns a [Errno 13] Permission Denied</p>
  
  <pre><code>&gt; Running virtualenv with interpreter /Users/Username/anaconda/lib/python3.5
  &gt; Traceback (most recent call last):   File "/usr/local/bin/virtualenv",
  &gt; line 11, in &lt;module&gt;
  &gt;     sys.exit(main())   File "/Library/Python/2.7/site-packages/virtualenv.py", line 790, in main
  &gt;     popen = subprocess.Popen([interpreter, file] + sys.argv[1:], env=env)   File
  &gt; "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py",
  &gt; line 710, in __init__
  &gt;     errread, errwrite)   File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py",
  &gt; line 1335, in _execute_child
  &gt;     raise child_exception
  OSError: [Errno 13] Permission denied
  </code></pre>
  
  <blockquote>
    <p>for: virtualenv -p /Users/Username/anaconda/bin/python3.5 venv</p>
  </blockquote>
  
  <p>there seems to be another type of error...</p>
  
  <pre><code>Running virtualenv with interpreter /Users/Username/anaconda/bin/python3.5
  Using base prefix '/Users/Username/anaconda'
  New python executable in venv/bin/python3.5
  Not overwriting existing python script venv/bin/python (you must use venv/bin/python3.5)
  ERROR: The executable venv/bin/python3.5 is not functioning
  ERROR: It thinks sys.prefix is '/Users/Username/.../targetfolder' (should be '/Users/Username/.../targetfolder/venv')
  ERROR: virtualenv is not compatible with this system or executable
  </code></pre>