fixed linting error

Author: horike37

lib/yamlParser.js

@@ -13,8 +13,9 @@ module.exports = {
     const serverlessYmlPath = path.join(servicePath, 'serverless.yml');
     return this.serverless.yamlParser
       .parse(serverlessYmlPath)
-      .then((serverlessFileParam) => {
-        return this.serverless.variables.populateObject(serverlessFileParam).then((parsedObject) => {
+      .then(serverlessFileParam =>
+        this.serverless.variables.populateObject(serverlessFileParam)
+        .then(parsedObject => {
           this.serverless.service.stepFunctions = {};
           this.serverless.service.stepFunctions.stateMachines
               = parsedObject.stepFunctions
@@ -39,8 +40,8 @@ module.exports = {
 
           this.serverless.variables.populateService(this.serverless.pluginManager.cliOptions);
           return BbPromise.resolve();
-        });
-      });
+        })
+      );
   },
 
   getAllStateMachines() {