Strict reason check for Failure class.

[proofit404]

• Strict check of the reason name in the Failure result class
• When substory injected or inherited, error protocol should expand to the superset of definitions.

[proofit404]

story = StoryFactory(failures=('invalid_code', 'invalid_id'))

class AcceptCode:

    @story
    def accept(I):
        I.check_code

    def check_code(self, ctx):
        return Failure('some reason')  # This should fail.