Every licensee granted a license under the terms of this ordinance shall be required to maintain both comprehensive public liability and automobile liability insurance underwritten by a company authorized to do business in the state against liability to the public in the amount as set by the City Council, and amended by resolution from time to time. These policies shall name the city as an additional insured and shall contain therein or have attached thereto by rider a provision that the insurer shall give notice to the city at least 10 days prior to the cancellation of the policy, in the event that the insurer should elect to cancel the same. The policy required, or a certificate executed by the insurer certifying to the existence of the insurance, shall be filed with the City Clerk prior to the issuance of any license or renewal thereof. The insurance shall be continuous until cancelled or shall expire April 30 of any year. Failure to maintain insurance as above provided shall be grounds for revocation of the license issued under this ordinance.