  
  from django.utils.itercompat import is_iterable
  
  
  class CheckRegistry(object):
  
      def __init__(self):
          self.registered_checks = []
  
      def register(self, *tags):
 
</s> remove from .. import Warning, register
 </s> add from .. import Warning, register, Tags </s> remove @register('compatibility')
 </s> add @register(Tags.compatibility) </s> remove         checks.register('admin')(check_admin_app)
 </s> add         checks.register(checks.Tags.admin)(check_admin_app) </s> remove from . import Error, register
 </s> add from . import Error, Tags, register </s> remove @register('models', 'signals')
 </s> add @register(Tags.models, Tags.signals)
class Tags(object):
    """
    Built-in tags for internal checks.
    """
    admin = 'admin'
    compatibility = 'compatibility'
    models = 'models'
    signals = 'signals'


  
  from django.utils.itercompat import is_iterable
  
  
class Tags(object):
    """
    Built-in tags for internal checks.
    """
    admin = 'admin'
    compatibility = 'compatibility'
    models = 'models'
    signals = 'signals'


  class CheckRegistry(object):
  
      def __init__(self):
          self.registered_checks = []
  
      def register(self, *tags):
keep keep keep add keep keep keep keep keep keep
 Fixed #22195 -- Used constants to define built-in tags for check framework.

Thanks Elvard for the patch. 
django/core/checks/registry.py