title: Tox virtualenv confusion
body: <p>Just starting out using tox for testing a library with Python 2.7 and 3.4.   After using the following <code>tox.ini</code> file I had two questions:</p>
  
  <pre><code>[tox]
  envlist = {py27,py3}
  sitepackages = True
  
  [testenv]
  deps= -rrequirements.txt
  commands = nosetests -w tests/ --with-coverage --cover-erase --cover-package=pyppa --with-xunit --xunit-file={toxinidir}/build/ppa-python-sdk_{envname}_unit_tests.xml
  coverage xml -o {toxinidir}/build/{envname}_coverage.xml
  </code></pre>
  
  <p>After running <code>tox</code> I had the following questions:</p>
  
  <ol>
  <li>The project depends on <code>numpy</code> and <code>scipy</code> which are both installed in my global environment, I thought that using <code>sitepackages = True</code> in the <code>tox.ini</code> file would prevent tox from installing these in the virutalenvironment and force it to use those in the global environment but tox installed the latest versions in the <code>.tox/</code> virtual environments for both 2.7 and 3.  Am I misunderstanding the <code>sitepackages</code> directive?</li>
  <li>Looking underneath the <code>.tox/</code> directory at the virtual environment directories I see the following (abbreviated) structure:</li>
  </ol>
  
  <p>.</p>
  
  <pre><code>  .tox/
      py27/
        include/
          python2.7/
        lib
          python2.7/
        ...
      py3/
        include/
          python2.7/
        lib
          python2.7/
        ...
  </code></pre>
  
  <p>I assure you that this is not a typo.  There are directories named <code>python2.7</code> under the py3 virtual environment <code>include</code> and <code>lib</code> sub-directories and these are the only sub-directories in <code>include</code> and <code>lib</code>.   Everything seems to work but I'm just curious as to why these directories are named this way.  Can someone shed some light on this?</p>
  
  <p>Thanks.</p>