title: Flask giving an internal server error instead of rendering 404
body: <p>In my Flask app, I set up a 404 handler like this:</p>
  
  <pre><code>@app.errorhandler(404)
  def page_not_found(e):
      return render_template('404.html'), 404
  </code></pre>
  
  <p>However, when a user goes to an unrecognized URL, the system gives an internal server error instead of rendering my <code>404</code> template.  Am I missing something?</p>