Merge branch '5.2' into 5.x

* 5.2:
  [travis] remove cache of composer.lock for deps=low
  Fix comment with typo

Tests/FilesystemTest.php

@@ -1762,7 +1762,7 @@ public function testCopyShouldKeepExecutionPermission()
     }
 
     /**
-     * Normalize the given path (transform each blackslash into a real directory separator).
+     * Normalize the given path (transform each forward slash into a real directory separator).
      */
     private function normalize(string $path): string
     {