In updating CircuitPython with the newer versions of micropython, the functionality for getting slice indices was inadvertently disabled.

There is a new flag, MICROPY_PY_BUILTINS_SLICE_INDICES, that is used in objslice.c for turning indices functionality on/off. This flag is currently off so slices no longer support getting indices.

This is a problem in pypixelbuf (PR and discussion).

@jepler Asked if I could submit this issue in CP so it can be addressed.