code: def post_create_app(cls, app, **settings):
          
          register_errorhandler = settings.pop('register_errorhandler', True)
  
          if register_errorhandler:
              AppException.register_errorhandler(app)
  
          return app
docs: Register the errorhandler for the AppException to the passed in
          App.
  
          Args:
              app (fleaker.base.BaseApplication): A Flask application that
                  extends the Fleaker Base Application, such that the hooks are
                  implemented.
  
          Kwargs:
              register_errorhandler (bool): A boolean indicating if we want to
                  automatically register an errorhandler for the
                  :class:`AppException` exception class after we create this App.
                  Pass ``False`` to prevent registration. Default is ``True``.
  
  
          Returns:
              fleaker.base.BaseApplication: Returns the app it was given.