In pleading to a preceding pleading, a party shall set forth affirmatively accord and satisfaction, arbitration and award, assumption of risk, contributory negligence, discharge in bankruptcy, duress, estoppel, failure of consideration, fraud, illegality, injury by fellow servant, laches, license, payment, release, res judicata, statute of frauds, statute of limitations, waiver, and any other matter constituting an avoidance or affirmative defense. Where the suit is on an insurance contract which insures against certain general hazards, but contains other provisions limiting such general liability, the party suing on such contract shall never be required to allege that the loss was not due to a risk or cause coming within any of the exceptions specified in the contract, nor shall the insurer be allowed to raise such issue unless it shall specifically allege that the loss was due to a risk or cause coming within a particular exception to the general liability; provided that nothing herein shall be construed to change the burden of proof on such issue as it now exists.