title: set pytest arg for tox but not direct pytest
body: <p>I'd tox to run pytest by default with some argument (<code>-n 2</code>) but I don't want that argument to be used by default if I just type <code>pytest ...</code> to run pytest directly. Is this possible?</p>
  
  <p>If I include this:</p>
  
  <pre><code>[pytest]
  addopts=-n 2
  </code></pre>
  
  <p>in <code>tox.ini</code>, then <code>tox</code> uses the option (as desired), but also makes <code>pytest</code> use the option if I just run <code>pytest ...</code> not through tox (not desired).</p>
  
  <p>I tried adding a <code>pytest.ini</code>, but then the defaults in <code>tox.ini</code> aren't used at all (whether running via <code>tox</code> or not).</p>
  
  <p>Any help?</p>