Merge branch '2.8' into 3.0

* 2.8:
  fixed typo
  fixed typo
  Fixed a minor XML issue in a translation file
  Fix merge
  Fix merge
  Fix merge
  Fix merge
  Update twig.html.twig
  PhpUnitNoDedicateAssertFixer results
  Improve Norwegian translations
  [2.7] [FrameworkBundle] minor fix tests added by #17569
  Fixed the antialiasing of the toolbar text
  Simplify markdown for PR template
  fixed CS
  fixed CS
  documented the $url parameter better
  [Form] add test for ArrayChoiceList handling null
  [Form] fix edge cases with choice placeholder
  register commands from kernel when accessing list
  Update FileSystem

Author: fabpot

Tests/CacheWarmer/CacheWarmerTest.php

@@ -32,7 +32,7 @@ public function testWriteCacheFileCreatesTheFile()
         $warmer = new TestCacheWarmer(self::$cacheFile);
         $warmer->warmUp(dirname(self::$cacheFile));
 
-        $this->assertTrue(file_exists(self::$cacheFile));
+        $this->assertFileExists(self::$cacheFile);
     }
 
     /**