At any time after the transmission of the diagram and assessment to the city tax collector or city auditor, the city council may let the contract for making such improvement. If the proceeding was commenced before the street lighting system referred to in the resolution of intention was installed or ordered installed, then such contract shall not be awarded until the street lighting system is installed or is duly ordered installed by the city council. If the installation of such proposed lighting system is abandoned, then the proceedings under this part shall be abandoned.