new_contents: from django.utils.hashcompat import md5_constructor
  from django.utils.http import urlquote
  
  
  def make_template_fragment_key(fragment_name, vary_on):
      # Build a unicode key for this fragment and all vary-on's.
      args = md5_constructor(u':'.join([urlquote(var) for var in vary_on]))
      cache_key = 'template.cache.%s.%s' % (fragment_name, args.hexdigest())
      return cache_key
  
subject: add (backported) make_template_fragment_key