[ticket/15257] Provide extension not enableable messages

PHPBB3-15257

tests/extension/ext/vendor5/foo/ext.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace vendor5\foo;
+
+class ext extends \phpbb\extension\base
+{
+	static public $enabled;
+
+	public function is_enableable()
+	{
+		return array('Reason 1', 'Reason 2');
+	}
+
+	public function enable_step($old_state)
+	{
+		self::$enabled = true;
+		return self::$enabled;
+	}
+}