new_contents: import md5
  
  from django import template
  
  register = template.Library()
  
  
  @register.filter('gravatar_url')
  def gravatar_url(email):
      hash = md5.new(email).hexdigest()
      return '<img class="avatar" src="http://www.gravatar.com/avatar/%s" />' % (hash, )
  
subject: add gravatar_url filter