Initial import from Alltube app

Removed dependency on Config and LocaleManager classes
Avoid using generic exceptions

classes/exceptions/AvconvException.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace Alltube\Library\Exception;
+
+use Throwable;
+
+/**
+ * Can't find avconv or ffmpeg.
+ */
+class AvconvException extends AlltubeLibraryException
+{
+    /**
+     * AvconvException constructor.
+     * @param string $path Path to avconv or ffmpeg.
+     */
+    public function __construct($path)
+    {
+        parent::__construct("Can't find avconv or ffmpeg at " . $path . '.');
+    }
+}