Any bond or other evidence of indebtedness issued under the provisions of any act repealed by this Code which is outstanding and unpaid on the effective date of this Code shall be amortized and retired by taxation or revenue in the manner provided by the act under which such indebtedness was incurred, notwithstanding the repeal of such act.
     However, the provisions of this section shall not be construed to prevent the refunding of any such indebtedness under the provisions of this Code or as may be otherwise provided by law.