lib/plugins/aws/package/compile/functions/index.js/AwsCompileFunctions/downloadPackageArtifacts
class AwsCompileFunctions:  downloadPackageArtifacts() {
    const allFunctions = this.serverless.service.getAllFunctions();
    return BbPromise.each(allFunctions, functionName => this.downloadPackageArtifact(functionName));
  }