Fix 7.2 compat layer

Author: nicolas-grekas

Tests/AppVariableTest.php

@@ -44,6 +44,9 @@ public function testEnvironment()
         $this->assertEquals('dev', $this->appVariable->getEnvironment());
     }
 
+    /**
+     * @runInSeparateProcess
+     */
     public function testGetSession()
     {
         $request = $this->getMockBuilder('Symfony\Component\HttpFoundation\Request')->getMock();

composer.json

@@ -23,6 +23,7 @@
         "symfony/asset": "~2.7",
         "symfony/finder": "~2.3",
         "symfony/form": "~2.7.30|^2.8.23",
+        "symfony/http-foundation": "~2.7.36|^2.8.29",
         "symfony/http-kernel": "~2.3",
         "symfony/intl": "~2.3",
         "symfony/routing": "~2.2",