title: Monkey patch Django runserver command
body: <p>I want to add <code>--env=prod/beta/alpha/dev</code> to <code>runserver</code> so i can do <code>python manage.py runserver --env=prod</code> for example.</p>
  
  <p>I've tried to add to <code>settings.py</code>:</p>
  
  <pre><code>parser = CommandParser(None)
  parser.add_argument('--env')
  parser.add_argument('args', nargs='*')  # catch-all
  
  try:
      options, args = parser.parse_known_args(sys.argv[2:])
  except CommandError:
      pass  # Ignore any option errors at this point.
  
  APP_ENV = options.env or 'dev' 
  </code></pre>
  
  <p>But I got:</p>
  
  <pre><code>usage: manage.py runserver [-h] [--version] [-v {0,1,2,3}]
                         [--settings SETTINGS] [--pythonpath PYTHONPATH]
                         [--traceback] [--no-color] [--ipv6] [--nothreading]
                         [--noreload] [--nostatic] [--insecure]
                         [addrport]
  manage.py runserver: error: unrecognized arguments: --env=beta
  </code></pre>
  
  <p>Any idea how can I monkey patch <code>runserver</code>?</p>