migration symfony 5 4 (#300)

* symfony 5.4 (diff dev)

* symfony 5.4 (working)

* symfony 5.4 (update autoload)

* symfony 5.4 (remove swiftmailer mailer implementation)

* symfony 5.4 (php doc and split Global accessor class)


### Impacted packages:

composer require php:">=7.2.5 <8.0.0" symfony/console:5.4.* symfony/dotenv:5.4.* symfony/framework-bundle:5.4.* symfony/twig-bundle:5.4.* symfony/yaml:5.4.* --update-with-dependencies

composer require symfony/stopwatch:5.4.* symfony/web-profiler-bundle:5.4.* --dev --update-with-dependencies

lib/symfony/http-kernel/Event/ExceptionEvent.php

@@ -0,0 +1,76 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\HttpKernel\Event;
+
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpKernel\HttpKernelInterface;
+
+/**
+ * Allows to create a response for a thrown exception.
+ *
+ * Call setResponse() to set the response that will be returned for the
+ * current request. The propagation of this event is stopped as soon as a
+ * response is set.
+ *
+ * You can also call setThrowable() to replace the thrown exception. This
+ * exception will be thrown if no response is set during processing of this
+ * event.
+ *
+ * @author Bernhard Schussek <bschussek@gmail.com>
+ */
+final class ExceptionEvent extends RequestEvent
+{
+    private $throwable;
+
+    /**
+     * @var bool
+     */
+    private $allowCustomResponseCode = false;
+
+    public function __construct(HttpKernelInterface $kernel, Request $request, int $requestType, \Throwable $e)
+    {
+        parent::__construct($kernel, $request, $requestType);
+
+        $this->setThrowable($e);
+    }
+
+    public function getThrowable(): \Throwable
+    {
+        return $this->throwable;
+    }
+
+    /**
+     * Replaces the thrown exception.
+     *
+     * This exception will be thrown if no response is set in the event.
+     */
+    public function setThrowable(\Throwable $exception): void
+    {
+        $this->throwable = $exception;
+    }
+
+    /**
+     * Mark the event as allowing a custom response code.
+     */
+    public function allowCustomResponseCode(): void
+    {
+        $this->allowCustomResponseCode = true;
+    }
+
+    /**
+     * Returns true if the event allows a custom response code.
+     */
+    public function isAllowingCustomResponseCode(): bool
+    {
+        return $this->allowCustomResponseCode;
+    }
+}