title: ImportError: No module named flask.ext.login even though Flask is installed
body: <p>I have installed Flask with:</p>
  
  <pre><code>pip install flask-debugtoolbar==0.10.0
  </code></pre>
  
  <p>When I <code>import flask</code> in Python, it works, but when I do <code>import flask.ext.login</code>, I get</p>
  
  <pre><code>ImportError: No module named flask.ext.login
  </code></pre>
  
  <p>Why can't I import this?</p>