lib/plugins/aws/logs/index.js/AwsLogs/extendedValidate
class AwsLogs:  extendedValidate() {
    this.validate();

    // validate function exists in service
    const lambdaName = this.serverless.service.getFunction(this.options.function).name;

    this.options.interval = this.options.interval || 1000;
    this.options.logGroupName = `/aws/lambda/${lambdaName}`;

    return BbPromise.resolve();
  }