Convert numpy/dask arrays from fixed width bytes to characters.

def bytes_to_char(arr):
    """Convert numpy/dask arrays from fixed width bytes to characters."""
    if arr.dtype.kind != 'S':
        raise ValueError('argument must have a fixed-width bytes dtype')

    if isinstance(arr, dask_array_type):
        import dask.array as da
        return da.map_blocks(_numpy_bytes_to_char, arr,
                             dtype='S1',
                             chunks=arr.chunks + ((arr.dtype.itemsize,)),
                             new_axis=[arr.ndim])
    else:
        return _numpy_bytes_to_char(arr)