249.955.  Amount of bonds and temporary notes, limitation not to exceed ten percent of assessed valuation of taxable tangible property. — The total amount of city or county general obligation bond indebtedness incurred for improvements under sections 249.925 to 249.955, including temporary notes issued pursuant to sections 249.925 to 249.955, shall not exceed ten percent of the assessed valuation of all taxable tangible property, as shown by the last completed property assessment for state or local purposes, within the district.