The legislative authority of a municipal corporation shall not agree by ordinance, contract, or otherwise with any person for the construction or extension of gasworks for manufacturing or supplying the municipal corporation or its inhabitants with gas, which gives or continues to such person the exclusive privilege of using the streets, lanes, commons, or alleys for the purpose of conveying gas to the municipal corporation or the citizens thereof, or which deprives the legislative authority of the right to designate, inspect, or regulate the kind of meter to be used for the correct measurement of the gas furnished under such agreement, or which does not specify the exact quality of the gas to be furnished, and reserve to the legislative authority the right to enforce an exact compliance with such specification under such rules as it prescribes. The legislative authority shall not make any such agreement which does not secure to it the right to purchase such works, and all the appurtenances belonging thereto, at any time within the existence of such contract or agreement.