Minor: wrap the inner error on retried transactions and return when deadline exceeded

package.json

@@ -64,6 +64,7 @@
     "ycsb": "node ./benchmark/ycsb.js  run -P ./benchmark/workloada -p table=usertable -p cloudspanner.instance=ycsb-instance -p operationcount=100 -p cloudspanner.database=ycsb"
   },
   "dependencies": {
+    "@google-cloud/common": "^0.23.0",
     "@google-cloud/common-grpc": "^0.7.1",
     "@google-cloud/paginator": "^0.1.0",
     "@google-cloud/projectify": "^0.3.0",

src/transaction.js

@@ -17,6 +17,7 @@
 'use strict';
 
 const {promisifyAll} = require('@google-cloud/promisify');
+const common = require('@google-cloud/common');
 const extend = require('extend');
 const gax = require('google-gax');
 const is = require('is');
@@ -40,6 +41,11 @@ const TransactionRequest = require('./transaction-request');
  */
 const UNKNOWN = 2;
 
+/** 
+ * the gRPC `DEADLINE_EXCEEDED` error code.
+ */
+const DEADLINE_EXCEEDED = 4;
+
 /**
  * The gRPC `ABORTED` error code.
  *
@@ -720,10 +726,11 @@ class Transaction extends TransactionRequest {
    * @return {object}
    */
   static createDeadlineError_(err) {
-    return extend({}, err, {
-      code: 4,
-      message: 'Deadline for Transaction exceeded.',
-    });
+    let apiError =  new common.util.ApiError('Deadline for Transaction exceeded.')
+    apiError.code = DEADLINE_EXCEEDED
+    apiError.errors.push(err)
+
+    return apiError;
   }
   /**
    * Extracts retry delay and formats into milliseconds.