It shall be the duty of the city comptroller, from twenty (20) to sixty (60) days prior to the expiration of the license period, to cause a written notice to be mailed to each licensee directing the attention of such licensee to the fact that a new license will be required on the day following the expiration of his existing license, and directing his attention also to the amount of the license fee and to the penalty for failure to procure a license in accordance with the provisions of this code governing the issuance of such license. Failure on the part of the city comptroller to cause such notice to be mailed to each licensee shall not, however, excuse the licensee from a failure to secure a new license or a renewal thereof, nor shall it be a defense to a suit brought by the city to recover the penalty for a violation of the provision of this code under which the licensee is required to obtain a license. (1977 Code)