Merge branch '5.1' into 5.2

* 5.1:
  Use ::class keyword when possible

Author: fabpot

Tests/Extension/TranslationExtensionTest.php

@@ -49,14 +49,14 @@ public function testTrans($template, $expected, array $variables = [])
 
     public function testTransUnknownKeyword()
     {
-        $this->expectException('Twig\Error\SyntaxError');
+        $this->expectException(\Twig\Error\SyntaxError::class);
         $this->expectExceptionMessage('Unexpected token. Twig was looking for the "with", "from", or "into" keyword in "index" at line 3.');
         $this->getTemplate("{% trans \n\nfoo %}{% endtrans %}")->render();
     }
 
     public function testTransComplexBody()
     {
-        $this->expectException('Twig\Error\SyntaxError');
+        $this->expectException(\Twig\Error\SyntaxError::class);
         $this->expectExceptionMessage('A message inside a trans tag must be a simple text in "index" at line 2.');
         $this->getTemplate("{% trans %}\n{{ 1 + 2 }}{% endtrans %}")->render();
     }