Cannot build an addon

[andytompkins]

Hi,
At my organization we would dearly like to use ember-twiddle in an internal fashion because we have proprietary (UNLICENSED) code that we would like to share with each other in the form of twiddles. To make this work, I need to get a few of our addons setup so they could be used to create twiddles. I have the main frontend software running with gatekeeper and working fine with our internal Github enterprise. The last piece is this backend/addon builder. I decided to hack together a small express server that would fill in for this backend, and just dump some pre-built addons into the right directory structure etc. That lead me to here, where I was trying to mimic what you have done to get addons building. I followed the process first and used docker (other than upload.js of course because that is very specific to your deployment scenario) and got some build errors. So I have tried again manually recreating what is happening with the docker setup, and I ended up with the same issue. The error is happening during ember build.
(Some of the following content was truncated for brevity.)

`app.vendorFiles['app-shims.js']`.
cleaning up...
Cleanup error.
tree.cleanup is not a function
TypeError: tree.cleanup is not a function
    at cleanupTree (builds/addon-builder/node_modules/broccoli-builder/lib/builder.js:203:17)
    at builds/addon-builder/node_modules/promise-map-series/index.js:11:14
    at tryCatch (builds/addon-builder/node_modules/rsvp/dist/rsvp.js:525:12)
    at invokeCallback (builds/addon-builder/node_modules/rsvp/dist/rsvp.js:538:13)
    at publish (builds/addon-builder/node_modules/rsvp/dist/rsvp.js:508:7)
    at flush (builds/addon-builder/node_modules/rsvp/dist/rsvp.js:2400:5)
    at _combinedTickCallback (internal/process/next_tick.js:73:7)
    at process._tickCallback (internal/process/next_tick.js:104:9)
Build failed.
The Broccoli Plugin: [BroccoliMergeTrees] failed with:
Error: Invalid tree found. You must supply a path or an object with a `.read` (deprecated) or `.rebuild` function: Array

I am wondering if you have any insight into this?