title: virtualenv activation doesn't work
body: <p>I've created a virtual environment with:</p>
  
  <pre><code>$ virtualenv my_ven_test
  </code></pre>
  
  <p>then let's activate the environment with:</p>
  
  <pre><code>$ source my_ven_test/bin/activate
  </code></pre>
  
  <p>now let's install a package:</p>
  
  <pre><code>(my_ven_test) $ pip install mysql-connector==2.1.3
  </code></pre>
  
  <p>This last line does not take effect. In fact if I check:</p>
  
  <pre><code>(my_ven_test) $ pip freeze
  </code></pre>
  
  <p>I see no package installed (as well as the <code>my_ven_test/lib/python/site-package</code> directory doesn't contain the mysql-connector package)</p>
  
  <p>Could you guide me in solving this issue?</p>
  
  <p>Some notes:</p>
  
  <ul>
  <li>python version: 2.7</li>
  <li>virtualenv version: 15.1.0</li>
  </ul>