Improvement on the documentation

[rijkerd]

Entered into an error while running the command Heroku local because of the environment variable. So could you add a simple note to anyone following up on the tutorial to consider that before running Heroku locally?

https://devcenter.heroku.com/articles/s3-upload-node

[YeahHuang]

I also met the error when running heroku local. My error is the configuration is not loaded into app.js. Could plz provide more information about the error you met?

My situation:
Error: Missing required key 'Bucket' in params
Reason: when running console.log(process.env.S3_BUCKET), it shows undefined
although running heroku config 's result is correct

 === obscure-headland-57151 Config Vars
AWS_ACCESS_KEY_ID:     xxxx
AWS_SECRET_ACCESS_KEY: xxxx
S3_BUCKET:             xxx