title: How do I customise url in RedirectView
body: <p>I'm using Django 1.5, trying to capture a param from url, then use this param to query an article id and redirect user to that article. </p>
  
  <p>Can I not specify new url in <code>url.py</code> and do something like below? But it just appends the url I want to use to the end of current url</p>
  
  <p>url.py</p>
  
  <pre><code>url(r'^external/(?P&lt;external_id&gt;\d+)/$', myView.as_view(), name='external-view')
  </code></pre>
  
  <p>views.py</p>
  
  <pre><code>class MyView(RedirectView):
      def get_redirect_url(self, **kwargs):
          external_id = kwargs['external_id']
          article_id = Article.objects.get(external_id=external_id).id
          domain = Site.objects.get_current().domain
          new_url = '{}/article/{}'.format(domain, article_id)
          return new_url
  </code></pre>