change to 405 Method Not Allowed

Signed-off-by: Olivier Lamy <olamy@apache.org>
diff --git a/redback-integrations/redback-rest/redback-rest-services/src/main/java/org/apache/archiva/redback/rest/services/DefaultUserService.java b/redback-integrations/redback-rest/redback-rest-services/src/main/java/org/apache/archiva/redback/rest/services/DefaultUserService.java
index afbb822..dde45e5 100644
--- a/redback-integrations/redback-rest/redback-rest-services/src/main/java/org/apache/archiva/redback/rest/services/DefaultUserService.java
+++ b/redback-integrations/redback-rest/redback-rest-services/src/main/java/org/apache/archiva/redback/rest/services/DefaultUserService.java
@@ -635,7 +635,7 @@
 
         if (Boolean.getBoolean(UserConfiguration.USER_REGISTRATION_DISABLE_KEY))
         {
-            throw new RedbackServiceException( new ErrorMessage("Registration Disabled"));
+            throw new RedbackServiceException( new ErrorMessage("Registration Disabled"), Response.Status.METHOD_NOT_ALLOWED.getStatusCode());
         }
 
         User user = userRegistrationRequest.getUser();