Add message to exception

svn path=/trunk/; revision=492

src/jsr311-api/src/javax/ws/rs/core/Variant.java

diff --git a/src/jsr311-api/src/javax/ws/rs/core/Variant.java b/src/jsr311-api/src/javax/ws/rs/core/Variant.java
index 5d5b3c1..ce69aa0 100644
--- a/src/jsr311-api/src/javax/ws/rs/core/Variant.java
+++ b/src/jsr311-api/src/javax/ws/rs/core/Variant.java
@@ -43,7 +43,7 @@
      */
     public Variant(MediaType mediaType, Locale language, String encoding) {
         if (mediaType==null && language==null && encoding==null)
-            throw new IllegalArgumentException();
+            throw new IllegalArgumentException("mediaType, language, encoding all null");
         this.encoding = encoding;
         this.language = language;
         this.mediaType = mediaType;