Prepare the UI Modules from a list of namespaced paths.

def _prepare_uimodules(self):
        """Prepare the UI Modules from a list of namespaced paths."""
        for key, value in self._config.get(config.UI_MODULES, {}).iteritems():
            self._config[config.UI_MODULES][key] = self._import_class(value)
        self._config[config.UI_MODULES] = dict(self._config[config.UI_MODULES] or {})