gulp-istanbul | Istanbul unit test coverage plugin for gulp | Frontend Framework library

It seems that your node-gyp requires java to be built correctly. The thing with Heroku's architecture is that it only provides you what you specify/need. Right now I don't think Heroku understands that it needs a JVM to run your application. So you should provide a buildpack. A build pack put very simply is a set of rules telling Heroku what to set-up, install and build. There is a buildpack for JVM called heroku/jvm. So, what you have to do is add this to your application through the dashboard or your CLI via heroku buildpacks:add heroku/jvm.

There is one more thing to do. Since your app requires javac at build time itself, we should pull up the build order for java/jvm . So in that case you should probably do heroku buildpacks:add --index 1 heroku/jvm. This puts the JVM buildpack at position 1 and pushes every other buildpack down the order.

Now when the app starts building, it first sets up the JVM (thus enabling javac for your instance) and then runs the NodeJS build. This build will now pick up the javac from the current instance and build accordingly.

Ref: Mulitple Buildpacks in Heroku

Try this.

Heroku will try to detect the kind of application you're deploying.

To determine how to start your app, Heroku first looks for a Procfile. If no Procfile exists for a Node.js app, we will attempt to start a default web process via the start script in your package.json.

I'm assuming there are no Procfile and that Heroku tries to run npm start.

Your start script is just the default gulp task, but because gulp isn't installed since it's not listed in the dependencies, it fails.

Heroku documentation about devDependencies

We set NPM_CONFIG_PRODUCTION to true by default to install production dependencies only. If you would like to install devDependencies, you can disable production mode:

Sounds like you might be using an incompatible version of nodeJS. That error message seems to indicate that the module in question (mach) is using the spread operator: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_operator

Maybe try updating your node version to one that supports the spread operator. Node 6+ is a good choice. Here's a great reference that stays up to date for feature support:

http://kangax.github.io/compat-table/es6/#test-spread_(...)_operator