SEC-2360: AbstractRememberMeServices provide message for Assert on key fieldd

web/src/main/java/org/springframework/security/web/authentication/rememberme/AbstractRememberMeServices.java

@@ -81,7 +81,7 @@ public abstract class AbstractRememberMeServices implements RememberMeServices,
     }
 
     public void afterPropertiesSet() throws Exception {
-        Assert.hasLength(key);
+        Assert.hasLength(key, "key cannot be empty or null");
         Assert.notNull(userDetailsService, "A UserDetailsService is required");
     }