title: How do I redirect to the www. version of my Flask site on Heroku?
body: <p>I've got a Python Flask app running on Heroku (Cedar stack) with two custom domains (one with and one without the www subdomain). I'd like to redirect all incoming requests to the www. version of the resource requested (the inverse of <a href="https://stackoverflow.com/questions/9350141/how-do-i-redirect-all-requests-with-urls-beginning-with-www-to-a-naked-domain">this question</a>). I think I need some WSGI middleware for this but I can't find a good example. </p>
  
  <p>How do I do this?</p>