commit 61b1225ab4478d694bf6ed91803e1d92c8f97d0f
Author: Moshe Weitzman <weitzman@tejasa.com>
Date:   Thu May 3 14:44:29 2018 -0400

    Make writable htkey file.

diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index 4d28eaa036..26ca135868 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -717,8 +717,10 @@ function drupal_generate_test_ua($prefix) {
     else {
       // Generate and save a new hash salt for a test run.
       // Consumed by drupal_valid_test_ua() before settings.php is loaded.
+      mkdir($key_dir, 0775, true);
+      chmod($key_dir, 0775);
       $private_key = Crypt::randomBytesBase64(55);
-      file_put_contents($key_file, $private_key);
+      file_put_contents($key_dir . '/.htkey', $private_key);
     }
     // The file properties add more entropy not easily accessible to others.
     $key = $private_key . filectime(__FILE__) . fileinode(__FILE__);