'Used to create the config attribute by the Flask constructor.
The `instance_relative` parameter is passed in from the constructor
of Flask (there named `instance_relative_config`) and indicates if
the config should be relative to the instance path or the root path
of the application.
.. versionadded:: 0.8'

def make_config(self, instance_relative=False):

    root_path = self.root_path
    if instance_relative:
        root_path = self.instance_path
    return self.config_class(root_path, self.default_config)
