"Where a landlord is obligated to make repairs during the term, actual or constructive notice of the need for repair is necessary to put him in default on his obligation, unless he agreed to repair without notice, or has actual knowledge, or reasonable opportunity to acquire knowledge, of the defect." (See also McNally v. Ward, 192 Cal.App.2d 871, 884 [ 14 Cal.Rptr. 260]; Yazzolino v. Jones, 153 Cal.App.2d 626, 637 [ 315 P.2d 107]; Farber v. Greenberg, 98 Cal.App. 675, 682 [ 277 P. 534]; Harris v. Joffe, 28 Cal.2d 418, 424 [ 170 P.2d 454].) Speaking of a landlord's covenant to repair, Professor Prosser says in his Law of Torts (2d ed.), page 475: "The jurisdictions which find a tort duty usually construe the lessor's covenant, in the absence of an express provision to the contrary, to mean merely that he must repair only within a reasonable time after he has been notified of the dangerous condition, or has otherwise discovered it."