Twisted, slots, and void method fails with "object has no attribute 'success'"

When generating Twisted code for a void method, the compiler accidentally assigns a value to the result.success field of the result object, even though, as a void method, there is no success value and the result object has no such field. If the slots option is not specified as well, this does not cause a problem, it just sets a new field that is never used. However, with the slots option, attempting to set this undefined field causes the error "object has no attribute 'success'"