new exception class for when something is not implemented or restricted on purpose

src/Exception/BehaviorImplementationRefusedException.php

@@ -0,0 +1,11 @@
+<?php
+namespace Gbili\Exception;
+
+/**
+ * Use this in a getter whose property has not been set yet
+ */
+class BehaviorImplementationRefusedException
+extends \Gbili\Exception\Exception
+{
+
+}