old_contents: # MIT License
  # Copyright (c) 2017 MassChallenge, Inc.
  from multidb import MasterSlaveRouter
  
  
  class APIRouter(object):
  
      def allow_migrate(
              self,
              db,
              app_label,
              model_name=None,
              **hints):
          """
          Make sure that we don't migrate
          apps shared by both accelerate and impact
          """
          if app_label in [
                  'auth',
                  'admin',
                  'sessions',
                  'simpleuser',
                  'sites',
                  'contenttypes']:
              return False
          return True
  
  
  class MasterSlaveAPIRouter(MasterSlaveRouter):
  
      def allow_migrate(
              self,
              db,
              app_label,
              model_name=None,
              **hints):
          """
          Make sure that we don't migrate
          apps shared by both accelerate and impact
          """
          allow_migrate = super().allow_migrate(
              db, app_label,
              model_name,
              **hints)
  
          if app_label in [
                  'auth',
                  'admin',
                  'sessions',
                  'simpleuser',
                  'sites',
                  'contenttypes']:
              return False
          return allow_migrate
  
new_contents: # MIT License
  # Copyright (c) 2017 MassChallenge, Inc.
  from multidb import MasterSlaveRouter
  
  
  class APIRouter(object):
  
      def allow_migrate(
              self,
              db,
              app_label,
              model_name=None,
              **hints):
          """
          Make sure that we don't migrate
          apps shared by both accelerate and impact
          """
          if app_label in [
                  'auth',
                  'admin',
                  'sessions',
                  'simpleuser',
                  'sites',
                  'thumbnail',
                  'contenttypes']:
              return False
          return True
  
  
  class MasterSlaveAPIRouter(MasterSlaveRouter):
  
      def allow_migrate(
              self,
              db,
              app_label,
              model_name=None,
              **hints):
          """
          Make sure that we don't migrate
          apps shared by both accelerate and impact
          """
          allow_migrate = super().allow_migrate(
              db, app_label,
              model_name,
              **hints)
  
          if app_label in [
                  'auth',
                  'admin',
                  'sessions',
                  'simpleuser',
                  'sites',
                  'contenttypes']:
              return False
          return allow_migrate
  
subject: add missing app from DB Router's list of excluded apps.