first commit

lib/pkp/classes/install/DowngradeNotSupportedException.php

@@ -0,0 +1,27 @@
+<?php
+
+/**
+ * @file classes/install/DowngradeNotSupportedException.php
+ *
+ * Copyright (c) 2014-2021 Simon Fraser University
+ * Copyright (c) 2000-2021 John Willinsky
+ * Distributed under the GNU GPL v3. For full terms see the file docs/COPYING.
+ *
+ * @brief Exception indicating an unsupported downgrade.
+ */
+
+namespace PKP\install;
+
+use Exception;
+use Throwable;
+
+class DowngradeNotSupportedException extends Exception
+{
+    /**
+     * Constructor
+     */
+    public function __construct(string $message = 'Downgrade not supported', int $code = 0, ?Throwable $previous = null)
+    {
+        parent::__construct($message, $code, $previous);
+    }
+}