Fix test_gc failure by fixing the bug test_gc found: __del__ methods were no longer preventing classes from being cleaned up by the cycle-gc, after Guido removed references to PyInstance_*.
Fix test_gc failure by fixing the bug test_gc found: __del__ methods were no
longer preventing classes from being cleaned up by the cycle-gc, after Guido
removed references to PyInstance_*.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator