Slate build errors when no config.yml file

[cshold]

Technically you shouldn't need a config.yml to do a local task like build. If you do you get this ugly output even though the task works as expected.

Message:
    `config.yml` does not exist. You need to add a config file before you can upload your theme to Shopify.
Stack:
Error: `config.yml` does not exist. You need to add a config file before you can upload your theme to Shopify.
    at processConfig (/Users/carsonshold/Documents/Projects/slate/node_modules/@shopify/slate-tools/lib/tasks/build-config.js:18:11)
    at Gulp.gulp.task (/Users/carsonshold/Documents/Projects/slate/node_modules/@shopify/slate-tools/lib/tasks/build-config.js:37:10)
    at module.exports (/Users/carsonshold/Documents/Projects/slate/node_modules/orchestrator/lib/runTask.js:34:7)
    at Gulp.Orchestrator._runTask (/Users/carsonshold/Documents/Projects/slate/node_modules/orchestrator/index.js:273:3)
    at Gulp.Orchestrator._runStep (/Users/carsonshold/Documents/Projects/slate/node_modules/orchestrator/index.js:214:10)
    at /Users/carsonshold/Documents/Projects/slate/node_modules/orchestrator/index.js:279:18
    at finish (/Users/carsonshold/Documents/Projects/slate/node_modules/orchestrator/lib/runTask.js:21:8)
    at module.exports (/Users/carsonshold/Documents/Projects/slate/node_modules/orchestrator/lib/runTask.js:60:3)
    at Gulp.Orchestrator._runTask (/Users/carsonshold/Documents/Projects/slate/node_modules/orchestrator/index.js:273:3)
    at Gulp.Orchestrator._runStep (/Users/carsonshold/Documents/Projects/slate/node_modules/orchestrator/index.js:214:10)
    at /Users/carsonshold/Documents/Projects/slate/node_modules/orchestrator/index.js:279:18
    at finish (/Users/carsonshold/Documents/Projects/slate/node_modules/orchestrator/lib/runTask.js:21:8)
    at module.exports (/Users/carsonshold/Documents/Projects/slate/node_modules/orchestrator/lib/runTask.js:60:3)
    at Gulp.Orchestrator._runTask (/Users/carsonshold/Documents/Projects/slate/node_modules/orchestrator/index.js:273:3)
    at Gulp.Orchestrator._runStep (/Users/carsonshold/Documents/Projects/slate/node_modules/orchestrator/index.js:214:10)
    at Gulp.Orchestrator.start (/Users/carsonshold/Documents/Projects/slate/node_modules/orchestrator/index.js:134:8)

Why should this be fixed?

I'm writing up some Slate usage docs that suggest running slate build before the steps of creating an app and config file. Quicker to see it work = more trust in the tool (or so is my thinking).

If we can remove that error from build we're golden.

cc @Shopify/themes-fed
@macdonaldr93 @m-ux

[NathanPJF]

Yep, this makes sense to me. Ideally you can run slate build and just get a warning that you have no config file, but have the build still happen.

[NathanPJF]

Possibly related: Shopify/slate-cli#118