Upon the taking effect of the ordinance the mayor and the city clerk or other proper official shall execute, in the name and on behalf of the city, the lease or conveyance directed thereby. The lessee or grantee shall accept and execute the instrument within ten days after notice of its execution by the city or forfeit to the city, the amount of the check or deposit accompanying his or her bid: PROVIDED, That if litigation in good faith is instituted within ten days to determine the rights of the parties, no forfeiture shall take place unless the lessee or grantee fails for five days after the termination of the litigation in favor of the city to accept and execute the lease or conveyance.