native_image.rb.patch

diff --git a/lib/sle2docker/native_image.rb b/lib/sle2docker/native_image.rb
index 955895e..ffb8b5d 100644
--- a/lib/sle2docker/native_image.rb
+++ b/lib/sle2docker/native_image.rb
@@ -48,10 +48,18 @@ module Sle2Docker
       @metadata     = parse_metadata_file("#{match['metadata_file']}.metadata")
       @repository   = @metadata['image']['name']
       @tag          = @metadata['image']['tags'][0]
+      verify_tag
       @build        = match['build']
       @image_id     = "#{@repository}:#{@tag}"
     end
 
+    def verify_tag
+      @tag.empty? &&
+         raise(DockerTagError,
+               "First tag in metadata file not a valid tag.\n" +
+               "Please check your kiwi configuration and set a valid tag.")
+    end
+
     def parse_metadata_file(metadata)
       file = File.read(
         File.join(NativeImage::IMAGES_DIR, metadata)