'Open the registry file. May raise OSError'

def _open(self):

    if os.path.exists(self._reg_path):
        reg_file = file(self._reg_path)
        app_list = json.load(reg_file)
        reg_file.close()
        for app_json in app_list:
            app_json.setdefault('author', 'Unknown')
            app = HueApp.create(app_json)
            self._apps[app.name] = app
    self._initialized = True
