Add exceptions from frontend

exceptions/updates/MDFileUploadNotAcceptedException.php

@@ -0,0 +1,22 @@
+<?PHP
+declare(strict_types = 1);
+
+/**
+ * Custom exception class for invalid page parameters, which must be values of a
+ * preset list of allowed values.
+ */
+class MDFileUploadNotAcceptedException extends Exception {
+
+    /**
+     * Error message.
+     *
+     * @return string
+     */
+    public function errorMessage() {
+        //error message
+        $errorMsg = $this->getMessage();
+        return $errorMsg;
+
+    }
+
+}