Merge branch '5.4' into 6.0

* 5.4:
  Simplify some code with null coalesce operator
  Don't use deprecated TestLogger class

Author: derrabus

Util/GitRepository.php

@@ -95,7 +95,7 @@ private static function exec(string $command, string $customErrorMessage = null)
         exec(sprintf('%s 2>&1', $command), $output, $result);
 
         if (0 !== $result) {
-            throw new RuntimeException(null !== $customErrorMessage ? $customErrorMessage : sprintf('The "%s" command failed.', $command));
+            throw new RuntimeException($customErrorMessage ?? sprintf('The "%s" command failed.', $command));
         }
 
         return $output;