title: How can I detect Heroku's environment?
body: <p>I have a Django webapp, and I'd like to check if it's running on the Heroku stack (for conditional enabling of debugging, etc.) Is there any simple way to do this? An environment variable, perhaps?</p>
  
  <p>I know I can probably also do it the other way around - that is, have it detect if it's running on a developer machine, but that just doesn't "sound right".</p>