Fix for a fatal error when system temp dir is not available

src/Composer/Console/Application.php

@@ -188,7 +188,7 @@ class Application extends BaseApplication
             }
 
             // Check system temp folder for usability as it can cause weird runtime issues otherwise
-            Silencer::call(function() {
+            Silencer::call(function () use ($io) {
                 $tempfile = sys_get_temp_dir() . '/temp-' . md5(microtime());
                 if (!(file_put_contents($tempfile, __FILE__) && (file_get_contents($tempfile) == __FILE__) && unlink($tempfile) && !file_exists($tempfile))) {
                     $io->writeError(sprintf('<error>PHP temp directory (%s) does not exist or is not writable to Composer. Set sys_temp_dir in your php.ini</error>', sys_get_temp_dir()));