N°2651 rollback gitignore for lib tests dirs

Too dangerous ! We'll work properly on this but for 2.8

lib/symfony/debug/Tests/Fixtures/ToStringThrower.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace Symfony\Component\Debug\Tests\Fixtures;
+
+class ToStringThrower
+{
+    private $exception;
+
+    public function __construct(\Exception $e)
+    {
+        $this->exception = $e;
+    }
+
+    public function __toString()
+    {
+        try {
+            throw $this->exception;
+        } catch (\Exception $e) {
+            // Using user_error() here is on purpose so we do not forget
+            // that this alias also should work alongside with trigger_error().
+            return trigger_error($e, E_USER_ERROR);
+        }
+    }
+}