Fixed a unit test

tests/PHPUnit/Unit/Tracker/RequestTest.php

@@ -464,9 +464,16 @@ class RequestTest extends UnitTestCase
 
     public function test_getBrowserLanguage_ShouldReturnADefaultLanguageInCaseNoneIsSet()
     {
+        $envLanguage = getenv('LANG');
+        putenv('LANG=en');
+
         $lang = $this->request->getBrowserLanguage();
         $this->assertNotEmpty($lang);
         $this->assertTrue(2 <= strlen($lang) && strlen($lang) <= 10);
+
+        if ($envLanguage !== false) {
+            putenv('LANG=' . $envLanguage);
+        }
     }
 
     public function test_makeThirdPartyCookie_ShouldReturnAnInstanceOfCookie()