title: Always require stage parameter for Serverless framework
body: <p>Is there a way to make Serverless abort execution if the stage is not given?</p>
  
  <p>Looks like it defaults to "dev", which is not preferred in a multi-environment setup where a "default" environment doesn't exist.</p>
  
  <p>The closest I could get was reading a 'stage' config variable from a local file. Unfortunately Serverless still defaults to 'dev' if the stage variable is missing from the (existing) local file. It does give a warning for the missing variable, though.</p>
  
  <pre><code>provider:
    name: aws
    runtime: nodejs8.10
    region: eu-west-1
    stage: ${file(serverless-local.yml):stage}
  </code></pre>