fix: backwards compatibility with serverless < 3 (#170)

fixes #165

Author: mikejpeters

lib/plugin.js

@@ -11,9 +11,9 @@ const uploadDirectory = require('./upload');
 const validateClient = require('./validate');
 
 class Client {
-  constructor(serverless, cliOptions, { log }) {
+  constructor(serverless, cliOptions, { log } = {}) {
     this.error = serverless.classes.Error;
-    this.log = log;
+    this.log = log || serverless.cli.log.bind(serverless.cli);
     this.serverless = serverless;
     this.options = serverless.service.custom.client;
     this.cliOptions = cliOptions || {};
@@ -70,7 +70,7 @@ class Client {
 
     this.hooks = {
       'client:client': () => {
-        log(this.commands.client.usage);
+        this.log(this.commands.client.usage);
       },
       'client:deploy:deploy': () => {
         return this._processDeployment();