small cleanup:

- be explicit when discarding returned errors from .Close(), etc.
- remove named return values from funcs when naked return not used
- fix some "err" shadowing when redeclaration not needed

internal/backend/local/local.go

@@ -118,7 +118,7 @@ func (b *Local) IsNotExist(err error) bool {
 }
 
 // Save stores data in the backend at the handle.
-func (b *Local) Save(ctx context.Context, h restic.Handle, rd io.Reader) (err error) {
+func (b *Local) Save(ctx context.Context, h restic.Handle, rd io.Reader) (error) {
 	debug.Log("Save %v", h)
 	if err := h.Valid(); err != nil {
 		return err