storage: checkPreconditions is now async

src/storage/interface.js

@@ -34,7 +34,7 @@ exports = module.exports = {
     injectPrivateFields
 };
 
-var assert = require('assert'),
+const assert = require('assert'),
     BoxError = require('../boxerror.js'),
     DataLayout = require('../datalayout.js'),
     EventEmitter = require('events');
@@ -56,12 +56,9 @@ function getRootPath(apiConfig) {
     return '/';
 }
 
-function checkPreconditions(apiConfig, dataLayout, callback) {
+async function checkPreconditions(apiConfig, dataLayout) {
     assert.strictEqual(typeof apiConfig, 'object');
     assert(dataLayout instanceof DataLayout, 'dataLayout must be a DataLayout');
-    assert.strictEqual(typeof callback, 'function');
-
-    callback(null);
 }
 
 function upload(apiConfig, backupFilePath, sourceStream, callback) {