lib/plugins/aws/invokeLocal/index.js/AwsInvokeLocal/checkDockerImage
class AwsInvokeLocal:  checkDockerImage() {
    const runtime = this.getRuntime();

    return new BbPromise((resolve, reject) => {
      const docker = spawn('docker', ['images', '-q', `lambci/lambda:${runtime}`]);
      let stdout = '';
      docker.stdout.on('data', (buf) => { stdout += buf.toString(); });
      docker.on('exit', error => (error ? reject(error) : resolve(Boolean(stdout.trim()))));
    });
  }