lib: add FileReaderException for file reader specific errors

refs #6722

library/Icinga/Protocol/File/Exception/FileReaderException.php

@@ -0,0 +1,10 @@
+<?php
+
+namespace Icinga\Protocol\File;
+
+use RuntimeException;
+
+/**
+ * Exception thrown if a file reader specific error occurs
+ */
+class FileReaderException extends RuntimeException {}