show error location in Rule.Artifact

Change-Id: Ic492a3e7d7a28633f96e808680ef695d33eb79f2
Reviewed-by: Jake Petroules <jake.petroules@petroules.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>