builder/qemu: passing tests

builder/qemu/builder.go

@@ -92,15 +92,15 @@ type config struct {
 	tpl             *packer.ConfigTemplate
 }
 
-func (b *Builder) Prepare(raws ...interface{}) error {
+func (b *Builder) Prepare(raws ...interface{}) ([]string, error) {
 	md, err := common.DecodeConfig(&b.config, raws...)
 	if err != nil {
-		return err
+		return nil, err
 	}
 
 	b.config.tpl, err = packer.NewConfigTemplate()
 	if err != nil {
-		return err
+		return nil, err
 	}
 	b.config.tpl.UserVars = b.config.PackerUserVars
 
@@ -361,10 +361,10 @@ func (b *Builder) Prepare(raws ...interface{}) error {
 	}
 
 	if errs != nil && len(errs.Errors) > 0 {
-		return errs
+		return nil, errs
 	}
 
-	return nil
+	return nil, nil
 }
 
 func (b *Builder) Run(ui packer.Ui, hook packer.Hook, cache packer.Cache) (packer.Artifact, error) {