old_contents: from django.http import HttpResponse, Http404
  import datetime
  
  def hello(request):
      return HttpResponse("Hello world")
  
  def current_datetime(request):
      now = datetime.datetime.now()
      html = "<html><head><title>time</title></head><body>It is new %s.</body></html>" % now
      return HttpResponse(html)
  def hours_ahead(request, offset):
      try:
          offset = int(offset)
      except ValueError:
          raise Http404()
      dt = datetime.datetime.now() + datetime.timedelta(hours=offset)
      #assert False
      html = "<html><body>In %s hour(s), it will be %s.</body></html>" % (offset, dt)
      return HttpResponse(html)
  
  
new_contents: from django.http import HttpResponse, Http404
  import datetime
  
  def hello(request):
      return HttpResponse("Hello world")
  
  
  
subject: remove something in ch03