Merge branch '3.4' into 4.0

* 3.4:
  [2.7] Fix issues found by PHPStan
  [Command] Fix upgrade guide example
  Add php_unit_dedicate_assert to PHPCS
  [WebProfilerBundle] Let fetch() cast URL to string
  improve FormType::getType exception message details
  [Intl] Update ICU data to 60.2
  [Console] fix a bug when you are passing a default value and passing -n would ouput the index
  [FrameworkBundle] fix merge of 3.3 into 3.4
  bumped Symfony version to 3.4.3
  updated VERSION for 3.4.2
  updated CHANGELOG for 3.4.2

Author: nicolas-grekas

FormRegistry.php

@@ -82,11 +82,14 @@ public function getType($name)
 
             if (!$type) {
                 // Support fully-qualified class names
-                if (class_exists($name) && in_array('Symfony\Component\Form\FormTypeInterface', class_implements($name))) {
-                    $type = new $name();
-                } else {
-                    throw new InvalidArgumentException(sprintf('Could not load type "%s"', $name));
+                if (!class_exists($name)) {
+                    throw new InvalidArgumentException(sprintf('Could not load type "%s": class does not exist.', $name));
                 }
+                if (!is_subclass_of($name, 'Symfony\Component\Form\FormTypeInterface')) {
+                    throw new InvalidArgumentException(sprintf('Could not load type "%s": class does not implement "Symfony\Component\Form\FormTypeInterface".', $name));
+                }
+
+                $type = new $name();
             }
 
             $this->types[$name] = $this->resolveType($type);