minor #31091 [TwigBridge] fix tests (nicolas-grekas)

This PR was merged into the 3.4 branch.

Discussion
----------

[TwigBridge] fix tests

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Follows https://github.com/twigphp/Twig/pull/2935

Commits
-------

33c6681585 [TwigBridge] fix tests

.travis.yml

@@ -48,6 +48,8 @@ before_install:
       # Enable Sury ppa
       sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 6B05F25D762E3157
       sudo add-apt-repository -y ppa:ondrej/php
+      sudo rm /etc/apt/sources.list.d/google-chrome.list
+      sudo rm /etc/apt/sources.list.d/mongodb-3.4.list
       sudo apt update
 
     - |

src/Symfony/Bridge/Twig/Tests/TokenParser/FormThemeTokenParserTest.php

@@ -30,9 +30,14 @@ class FormThemeTokenParserTest extends TestCase
     {
         $env = new Environment($this->getMockBuilder('Twig\Loader\LoaderInterface')->getMock(), ['cache' => false, 'autoescape' => false, 'optimizations' => 0]);
         $env->addTokenParser(new FormThemeTokenParser());
-        $stream = $env->tokenize(new Source($source, ''));
+        $source = new Source($source, '');
+        $stream = $env->tokenize($source);
         $parser = new Parser($env);
 
+        if (method_exists($expected, 'setSourceContext')) {
+            $expected->setSourceContext($source);
+        }
+
         $this->assertEquals($expected, $parser->parse($stream)->getNode('body')->getNode(0));
     }