[2.8] Fix issues reported by static analyse

Author: romainneutron

CacheWarmer/TemplateFinder.php

@@ -14,6 +14,7 @@
 use Symfony\Component\HttpKernel\KernelInterface;
 use Symfony\Component\Finder\Finder;
 use Symfony\Component\Templating\TemplateNameParserInterface;
+use Symfony\Component\Templating\TemplateReferenceInterface;
 use Symfony\Component\HttpKernel\Bundle\BundleInterface;
 
 /**