Merge branch '3.4' into 4.0

* 3.4:
  [Yaml] Fix regression when trying to parse multiline
  Add PHPDbg support to HTTP components
  bumped Symfony version to 2.8.38
  updated VERSION for 2.8.37
  updated CHANGELOG for 2.8.37
  bumped Symfony version to 2.7.45
  updated VERSION for 2.7.44
  update CONTRIBUTORS for 2.7.44
  updated CHANGELOG for 2.7.44
  Fix check of color support on Windows

Debug.php

@@ -42,7 +42,7 @@ class Debug
             error_reporting(E_ALL);
         }
 
-        if ('cli' !== PHP_SAPI) {
+        if (!\in_array(PHP_SAPI, array('cli', 'phpdbg'), true)) {
             ini_set('display_errors', 0);
             ExceptionHandler::register();
         } elseif ($displayErrors && (!ini_get('log_errors') || ini_get('error_log'))) {

ErrorHandler.php

@@ -547,14 +547,15 @@ class ErrorHandler
                 }
             }
         }
+        $exceptionHandler = $this->exceptionHandler;
+        $this->exceptionHandler = null;
         try {
-            if (null !== $this->exceptionHandler) {
-                return \call_user_func($this->exceptionHandler, $exception);
+            if (null !== $exceptionHandler) {
+                return \call_user_func($exceptionHandler, $exception);
             }
             $handlerException = $handlerException ?: $exception;
         } catch (\Throwable $handlerException) {
         }
-        $this->exceptionHandler = null;
         if ($exception === $handlerException) {
             self::$reservedMemory = null; // Disable the fatal error handler
             throw $exception; // Give back $exception to the native handler

Tests/ErrorHandlerTest.php

@@ -464,4 +464,17 @@ class ErrorHandlerTest extends TestCase
         $this->assertInstanceOf('Symfony\Component\Debug\Exception\ClassNotFoundException', $args[0]);
         $this->assertStringStartsWith("Attempted to load class \"Foo\" from the global namespace.\nDid you forget a \"use\" statement", $args[0]->getMessage());
     }
+
+    /**
+     * @expectedException \Exception
+     */
+    public function testCustomExceptionHandler()
+    {
+        $handler = new ErrorHandler();
+        $handler->setExceptionHandler(function ($e) use ($handler) {
+            $handler->handleException($e);
+        });
+
+        $handler->handleException(new \Exception());
+    }
 }