Revenue bonds issued under authority of sections 204.250 to 204.470 shall be payable solely from the revenues derived and to be derived from the operation of the sewerage system acquired, constructed, improved or extended in whole or in part from the proceeds of the bonds. No revenue bonds issued pursuant to sections 204.250 to 204.470 shall constitute an indebtedness of the common sewer district within the meaning of any constitutional or statutory restriction, limitation or provision. The face of each bond shall state in substance that the bond has been issued under the provisions of sections 204.250 to 204.470, that the taxing power of the common sewer district issuing the bond is not pledged to the payment thereof either as to principal or interest and that the bond and the interest thereon are payable solely from the revenues of the sewerage system for the benefit of which the bond was issued.