'We want to bind the CMSapp class to a specific AppHookConfig, but only one at a time
Checking for the runtime attribute should be a sane fix'

def __new__(cls):

    if cls.app_config:
        if (getattr(cls.app_config, 'cmsapp', None) and (cls.app_config.cmsapp != cls)):
            raise RuntimeError(('Only    one    AppHook    per    AppHookConfiguration    must    exists.\nAppHook    %s    already    defined    for    %s    AppHookConfig' % (cls.app_config.cmsapp.__name__, cls.app_config.__name__)))
        cls.app_config.cmsapp = cls
    if hasattr(cls, 'urls'):
        if (not isinstance(cls.urls, property)):
            cls._urls = cls.urls
            cls.urls = cls.legacy_urls
    else:
        cls.urls = cls.legacy_urls
    if hasattr(cls, 'menus'):
        if (not isinstance(cls.menus, property)):
            cls._menus = cls.menus
            cls.menus = cls.legacy_menus
    else:
        cls.menus = cls.legacy_menus
    return super(CMSApp, cls).__new__(cls)
