Merge pull request #327 from josete89/patch-1

Update layer.js

Author: dschep

lib/layer.js

@@ -25,6 +25,9 @@ function zipRequirements() {
  * @return {Promise} empty promise
  */
 function createLayers() {
+  if (!this.serverless.service.layers) {
+    this.serverless.service.layers = {};
+  }
   this.serverless.service.layers['pythonRequirements'] = Object.assign(
     {
       artifact: path.join('.serverless', 'pythonRequirements.zip'),