Skip test if de_DE is not available.

Refs #9335

tests/TestCase/Utility/HashTest.php

@@ -1687,8 +1687,8 @@ class HashTest extends TestCase
         // get the current locale
         $oldLocale = setlocale(LC_COLLATE, '0');
 
-        // the de_DE.utf8 locale must be installed on the system where the test is performed
-        setlocale(LC_COLLATE, 'de_DE.utf8');
+        $updated = setlocale(LC_COLLATE, 'de_DE.utf8');
+        $this->skipIf($updated === false, 'Could not set locale to de_DE.utf8, skipping test.');
 
         $items = [
             ['Item' => ['entry' => 'Übergabe']],