old_contents: from django import template
  from django.contrib.messages.utils import get_level_tags
  from django.utils.encoding import force_text
  
  
  LEVEL_TAGS = get_level_tags()
  
  register = template.Library()
  
  
  @register.simple_tag()
  def get_message_tags(message):
      """
      Returns the message's level_tag prefixed with Bootstrap's "alert-" prefix
      along with any tags included in message.extra_tags
  
      Messages in Django >= 1.7 have a message.level_tag attr
      """
      level_tag = force_text(LEVEL_TAGS.get(message.level, ''), strings_only=True)
      if level_tag == u"error":
          level_tag = u"danger"
  
      alert_level_tag = u"alert-{tag}".format(tag=level_tag)
  
      tags = [alert_level_tag]
      extra_tags = force_text(message.extra_tags, strings_only=True)
      if extra_tags:
          tags.append(extra_tags)
  
      return u" ".join(tags)
  
new_contents: from django import template
  from django.contrib.messages.utils import get_level_tags
  from django.utils.encoding import force_text
  
  
  LEVEL_TAGS = get_level_tags()
  
  register = template.Library()
  
  
  @register.simple_tag()
  def get_message_tags(message):
      """
      Returns the message's level_tag prefixed with Bootstrap's "alert-" prefix
      along with any tags included in message.extra_tags
  
      Messages in Django >= 1.7 have a message.level_tag attr
      """
      level_tag = force_text(LEVEL_TAGS.get(message.level, ''), strings_only=True)
      if level_tag == u"error":
          level_tag = u"danger"
  
      if level_tag:
          alert_level_tag = u"alert-{tag}".format(tag=level_tag)
      else:
          alert_level_tag = None
  
      extra_tags = force_text(message.extra_tags, strings_only=True)
  
      if extra_tags and alert_level_tag:
          return u' '.join([extra_tags, alert_level_tag])
      elif extra_tags:
          return extra_tags
      elif alert_level_tag:
          return alert_level_tag
      return u''
  
subject: Handle instances where level_tag is undefined