Every written agreement hereafter made by one person to answer for the default of another shall subject such person to the liabilities of suretyship, and shall confer upon him the rights incident thereto, unless such agreement shall contain in substance the words: “This is not intended to be a contract of suretyship,” or unless each portion of such agreement intended to modify the rights and liabilities of suretyship shall contain in substance the words: “This portion of the agreement is not intended to impose the liability of suretyship.”