Issue #2332295 followup by klausi: Fixed Unicode requirements check not working with PHP 5.6.

core/lib/Drupal/Component/Utility/Unicode.php

@@ -163,8 +163,10 @@ public static function check() {
       static::$status = static::STATUS_ERROR;
       return 'mbstring.encoding_translation';
     }
-    // mbstring.http_input is deprecated and empty by default in PHP 5.6.
-    if (version_compare(PHP_VERSION, '5.6.0') == -1 && ini_get('mbstring.http_input') != 'pass') {
+    // mbstring.http_input and mbstring.http_output are deprecated and empty by
+    // default in PHP 5.6.
+    if (version_compare(PHP_VERSION, '5.6.0') == -1) {
+      if (ini_get('mbstring.http_input') != 'pass') {
         static::$status = static::STATUS_ERROR;
         return 'mbstring.http_input';
       }
@@ -172,6 +174,7 @@ public static function check() {
         static::$status = static::STATUS_ERROR;
         return 'mbstring.http_output';
       }
+    }
 
     // Set appropriate configuration.
     mb_internal_encoding('utf-8');