/usr/share/php/Symfony/Component/DependencyInjection/Loader/ is in php-symfony-dependency-injection 2.3.21+dfsg-4+deb8u3.
This file is owned by root:root, with mode 0o755.
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/usr/share/php/Symfony/Component/DependencyInjection/Loader/ClosureLoader.php
/usr/share/php/Symfony/Component/DependencyInjection/Loader/FileLoader.php
/usr/share/php/Symfony/Component/DependencyInjection/Loader/IniFileLoader.php
/usr/share/php/Symfony/Component/DependencyInjection/Loader/PhpFileLoader.php
/usr/share/php/Symfony/Component/DependencyInjection/Loader/XmlFileLoader.php
/usr/share/php/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php
/usr/share/php/Symfony/Component/DependencyInjection/Loader/schema/
/usr/share/php/Symfony/Component/DependencyInjection/Loader/schema/dic/
/usr/share/php/Symfony/Component/DependencyInjection/Loader/schema/dic/services/
/usr/share/php/Symfony/Component/DependencyInjection/Loader/schema/dic/services/services-1.0.xsd