old_contents: class ProdMonDBRouter(object):
      def db_for_read(self, model, **hints):
          if model._meta.app_label == 'auth':
              return 'default'
          if model._meta.app_label == 'prodtask':
              return 'deft'
          if model._meta.app_label == 'art':
              return 'deft'
          if model._meta.app_label == 'panda':
              return 'panda'
          if model._meta.app_label == 'grisli':
              return 'grisli'
          if model._meta.app_label == "taskmon":
              return "deft_adcr"
          if model._meta.app_label == 'authtoken':
              return 'dev_db'
          if model._meta.app_label == 'dev':
              return 'dev_db'
          if model._meta.app_label == 'panda_dev':
              return 'panda_dev'
          return None
  
      def db_for_write(self, model, **hints):
          if model._meta.app_label == 'auth':
              return 'default'
          if model._meta.app_label == 'panda_dev':
              return 'panda_dev'
          if model._meta.app_label == 'prodtask':
              return 'deft'
          if model._meta.app_label == 'art':
              return 'deft'
          if model._meta.app_label == 'dev':
              return 'dev_db_wr'
          if model._meta.app_label == 'authtoken':
              return 'dev_db_wr'
          if model._meta.app_label == 'panda':
              return 'panda_wr'
          return None
  
      def allow_relation(self, obj1, obj2, **hints):
          if ((obj1._meta.app_label == 'prodtask') and (obj2._meta.app_label == 'dev')) or\
                  ((obj1._meta.app_label == 'dev') and (obj2._meta.app_label == 'dev')) or ((obj1._meta.app_label == 'auth') and (obj2._meta.app_label == 'authtoken')):
              return True
          return None
  
      def allow_migrate(self, db, model):
          return None
  
new_contents: class ProdMonDBRouter(object):
      def db_for_read(self, model, **hints):
          if model._meta.app_label == 'auth':
              return 'default'
          if model._meta.app_label == 'prodtask':
              return 'deft'
          if model._meta.app_label == 'art':
              return 'deft'
          if model._meta.app_label == 'panda':
              return 'panda'
          if model._meta.app_label == 'grisli':
              return 'grisli'
          if model._meta.app_label == "taskmon":
              return "deft_adcr"
          if model._meta.app_label == 'authtoken':
              return 'dev_db'
          if model._meta.app_label == 'dev':
              return 'dev_db'
          if model._meta.app_label == 'panda_dev':
              return 'panda_dev'
          return None
  
      def db_for_write(self, model, **hints):
          if model._meta.app_label == 'auth':
              return 'default'
          if model._meta.app_label == 'panda_dev':
              return 'panda_dev'
          if model._meta.app_label == 'prodtask':
              return 'deft'
          if model._meta.app_label == 'art':
              return 'deft'
          if model._meta.app_label == 'dev':
              return 'dev_db_wr'
          if model._meta.app_label == 'authtoken':
              return 'dev_db_wr'
          if model._meta.app_label == 'panda':
              return 'panda_wr'
          return None
  
      def allow_relation(self, obj1, obj2, **hints):
          if ((obj1._meta.app_label == 'prodtask') and (obj2._meta.app_label == 'dev')) or\
                  ((obj1._meta.app_label == 'dev') and (obj2._meta.app_label == 'dev')) or ((obj1._meta.app_label == 'auth') and (obj2._meta.app_label == 'authtoken')):
              return True
          return None
  
      def allow_migrate(self, db, app_label, model_name=None, **hints):
          return None
  
subject: prepare for Django2 migration