Node 4 doesn't expose fs.constants

Author: Maël Nison

src/util/fs.js

@@ -13,7 +13,11 @@ const globModule = require('glob');
 const os = require('os');
 const path = require('path');
 
-export const constants = fs.constants;
+export const constants = typeof fs.constants !== 'undefined' ? fs.constants : {
+    R_OK: fs.R_OK,
+    W_OK: fs.W_OK,
+    X_OK: fs.X_OK,
+};
 
 export const lockQueue = new BlockingQueue('fs lock');