Silence invasive deprecation warnings, opt-in for warnings

Yaml.php

@@ -58,7 +58,7 @@ public static function parse($input, $exceptionOnInvalidType = false, $objectSup
         // if input is a file, process it
         $file = '';
         if (strpos($input, "\n") === false && is_file($input)) {
-            trigger_error('The ability to pass file names to the '.__METHOD__.' method is deprecated since version 2.2 and will be removed in 3.0. Pass the YAML contents of the file instead.', E_USER_DEPRECATED);
+            @trigger_error('The ability to pass file names to the '.__METHOD__.' method is deprecated since version 2.2 and will be removed in 3.0. Pass the YAML contents of the file instead.', E_USER_DEPRECATED);
 
             if (false === is_readable($input)) {
                 throw new ParseException(sprintf('Unable to parse "%s" as the file is not readable.', $input));