Revenue bonds issued under the provisions of this act shall not constitute a debt of the Commonwealth of Virginia or of any other political subdivision thereof nor a pledge of the faith and credit of the Commonwealth or of any political subdivision thereof. Such bonds shall be payable solely from funds provided therefor from revenues. The issuance of revenue bonds under the provisions of this act shall not directly, indirectly, or contingently obligate the Commonwealth or any political subdivision thereof to the payment thereof or to the levy or pledge of any form of taxation whatever therefor. All such revenue bonds shall contain a statement on their face substantially to this effect.