LambdaFunction - Value of property Variables must be an object with String (or simple type) properties - node.js

Question

I am using serverless to deploy my Lambda based application. It was deploying just fine, and then it stopped for some reason. I paired down the entire package to the serverless.yml below and one function in the handler - but I keep getting this error:
Serverless Error ---------------------------------------
An error occurred: TestLambdaFunction - Value of property Variables must be an object with String (or simple type) properties.
Stack Trace --------------------------------------------
Here is the serverless.yml
# serverless.yml
service: some-api
provider:
name: aws
runtime: nodejs6.10
stage: prod
region: us-east-1
iamRoleStatements:
$ref: ./user-policy.json
environment:
config:
region: us-east-1
plugins:
- serverless-local-dev-server
- serverless-dynamodb-local
- serverless-step-functions
package:
exclude:
- .gitignore
- package.json
- README.md
- .git
- ./**.test.js
functions:
test:
handler: handler.test
events:
- http: GET test
resources:
Outputs:
NewOutput:
Description: Description for the output
Value: Some output value
Test Lambda Function in Package
#handler.test
module.exports.test = (event, context, callback) => {
callback(null, {
statusCode: 200,
body: JSON.stringify({
message: 'sadfasd',
input: event
})
})
}

Answer 1

Turns out, this issue does not have any relationship to the Lambda function. Here is the issue that caused the error.
This does NOT work:
environment:
config:
region: us-east-1
This DOES work:
environment:
region: us-east-1
Simply put, I don't think you can have more than one level in your yaml environment variables.
Even if you try sls print as a sanity check, this issue will not pop up. Only in sls deploy.
You have been warned, and hopefully saved!

Answer 2

Other thing that might cause this kind of error is using invalid yaml syntax.
It's easy to get confused about this.
Valid syntax for environment variables
environment:
key: value
Invalid syntax for environment variables
environment:
- key: value
Notice little dash in the code below?
In yaml syntax - means array and therefore, code below is interpreted as array, not object.
So that's why error tells "Value of property Variables must be an object with String (or simple type) properties."
This can be easily fixed by removing - in front of all keys.