Compare configuration to be merged with the one on the device.

        Compare executed candidate config with the running config and
        return a diff, assuming the loaded config will be merged with the
        existing one.

        :return:  Config diff.

def compare_config(self):
        """
        Compare configuration to be merged with the one on the device.

        Compare executed candidate config with the running config and
        return a diff, assuming the loaded config will be merged with the
        existing one.

        :return:  Config diff.
        """
        _show_merge = self._execute_config_show('show configuration merge')
        _show_run = self._execute_config_show('show running-config')

        diff = difflib.unified_diff(_show_run.splitlines(1)[2:-2], _show_merge.splitlines(1)[2:-2])
        return ''.join([x.replace('\r', '') for x in diff])