Merge branch '5.0' into 5.1

* 5.0:
  Fix abstract method name in PHP doc block
  Various cleanups
  [HttpClient] fix issues in tests
  Fixes sprintf(): Too few arguments in form transformer
  [Console] Fix QuestionHelper::disableStty()
  [Validator] Use Mime component to determine mime type for file validator
  validate subforms in all validation groups
  Update Hungarian translations
  Add meaningful message when Process is not installed (ProcessHelper)
  [PropertyAccess] Fix TypeError parsing again.
  [TwigBridge] fix fallback html-to-txt body converter
  [Security/Http] fix merge
  [ErrorHandler] fix setting $trace to null in FatalError
  [Form] add missing Czech validators translation
  [Validator] add missing Czech translations
  never directly validate Existence (Required/Optional) constraints

Author: nicolas-grekas

Data/Bundle/Reader/JsonBundleReader.php

@@ -46,7 +46,7 @@ public function read(string $path, string $locale)
         $data = json_decode(file_get_contents($fileName), true);
 
         if (null === $data) {
-            throw new RuntimeException(sprintf('The resource bundle "%s" contains invalid JSON: '.json_last_error_msg(), $fileName));
+            throw new RuntimeException(sprintf('The resource bundle "%s" contains invalid JSON: ', $fileName).json_last_error_msg());
         }
 
         return $data;