title: What's considered (in)appropriate use of request.env in rails?
body: <p>My understanding is that request.env stores info about user's or server's environment. Looking at a piece of ActionDispatch <a href="https://github.com/rails/rails/blob/5359262695b491422b18c565567e16ad50f6155e/actionpack/lib/action_dispatch/middleware/show_exceptions.rb#L74" rel="nofollow">code</a> I see it storing an exception, and it made me wonder if this is appropriate?</p>
  
  <p>That leads me to a more general question of what would be considered some (in)appropriate uses of using request.env?</p>