earlier coercion changes, not by rich comparisons.  When a coercion
function returns 1 (meaning it cannot do it), it should not INCREF the
arguments.  When no __coerce__() method was found, instance_coerce()
originally returned 0, pretending it did it.  Neil changed the return
value to 1, more accurately reflecting that it didn't do anything, but
forgot to take out the two INCREF calls.