archive: New() can't fail, so don't return an error type

It could fail if the system can't allocate memory or something
undeterministic like that, but in that case it's best to just let the
runtime panic.

internal/archive/archive.go

@@ -51,7 +51,7 @@ type Archive struct {
 	items           archiveItems
 }
 
-func New(format CompressFormat, level CompressLevel) (*Archive, error) {
+func New(format CompressFormat, level CompressLevel) *Archive {
 	buf := new(bytes.Buffer)
 	archive := &Archive{
 		cpioWriter:      cpio.NewWriter(buf),
@@ -60,7 +60,7 @@ func New(format CompressFormat, level CompressLevel) (*Archive, error) {
 		compress_level:  level,
 	}
 
-	return archive, nil
+	return archive
 }
 
 type archiveItem struct {