Task.Close should return error, and Process... should handle and/or propagate that error.

[gfr10598]

etl/task/task.go

Line 66 in 5caa9cb

func (tt *Task) Close() {

Currently, these errors are dropped - not reported to Gardener.

Among these errors are GCS write errors, reported on

etl/storage/rowwriter.go

Lines 168 to 169 in 5caa9cb

	attr, err := rw.o.Update(ctx, oa)
	log.Println(attr, err)

[gfr10598]

There are also insufficient permission errors that should be propagated.

[laiyi-ohlsen]

@stephen-soltesz