This report makes no sense to me; at least in Python 2.X, PyObject_Del
removes a chunk of memory from the object heap.  It's designed to be
used from dealloc implementations, to release the actual memory (either
directly, or as the default implementation for the tp_free slot).  It
can also be used in constructors, to destroy an object that was just
created if something goes wrong.

If you change PyObject_Del to Py_DECREF nillywilly, things will indeed
crash.

(with the original 2.5 code, I cannot see how a non-string argument to
finditer() can result in a call to scanner_dealloc(); the argument will
be rejected by getstring(), which causes state_init() to return, which
causes pattern_scanner() to free the object it just created, and return.)