build dev failed error when starting ionic serve

[jgw96]

Short description of the problem:

When starting ionic serve i get this output

ionic-hello-world@ watch /Users/justinwillis/Projects/ionicBeer
ionic-app-scripts watch

[09:53:46]  ionic-app-scripts 0.0.37 
[09:53:46]  watch started ... 
[09:53:46]  build dev started ... 
[09:53:46]  clean started ... 
[09:53:46]  clean finished in 25 ms 
[09:53:46]  copy started ... 
[09:53:46]  transpile started ... 
[09:53:53]  transpile finished in 6.99 s 
[09:53:53]  webpack started ... 
(node:27030) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): Error: [object Object]
[09:53:53]  copy finished in 7.38 s 
[09:54:00]  webpack finished in 7.25 s 
[09:54:00]  sass started ... 
[09:54:00]  build dev failed: [object Object] 
(node:27030) PromiseRejectionHandledWarning: Promise rejection was handled asynchronously (rejection id: 1)
[09:54:00]  watch ready in 14.49 s  ```

Note: this does not happen when using rollup

**Steps to reproduce:**
1. clone https://github.com/jgw96/ionicBeer
2. cd into project, run `npm install`, and run `ionic serve`

**Which @ionic/app-scripts version are you using?** 
latest master branch. I also get this with the latest `@beta` release.

[jgw96]

This has been fixed in the latest beta release.