def _exclude_on_fail(self, df):
        """Assign a selection of scenarios as `exclude: True` in meta"""
        idx = df if isinstance(df, pd.MultiIndex) else _meta_idx(df)
        self.meta.loc[idx, 'exclude'] = True
        logger().info('{} non-valid scenario{} will be excluded'
                      .format(len(idx), '' if len(idx) == 1 else 's'))
Assign a selection of scenarios as `exclude: True` in meta