functions-samples: Deploy Error: Failed to configure trigger GCS Bucket

Hi, I’m trying out the image resizing demo. Deployment throwing error:

 Deploy Error: Failed to configure trigger GCS Bucket: product_images

My images are inside product_images folder and my code looks like this:

exports.generateThumbnail = functions.storage.object().onChange(event => {
  const object = event.data;
  const fileBucket = object.bucket;
  const filePath = object.name;
  const contentType = object.contentType;
  const resourceState = object.resourceState;

  if(!filePath.match(/product_images/)) {
    console.log('not product_images bucket');
    return;
  }

  if (!contentType.startsWith('image/')) {
    console.log('This is not an image.');
    return;
  }

  const fileName = filePath.split('/').pop();
  // Exit if the image is already a thumbnail.
  if (fileName.startsWith('thumb_')) {
    console.log('Already a Thumbnail.');
    return;
  }

  if (resourceState === 'not_exists') {
    console.log('This is a deletion event.');
    return;
  }

  const bucket = gcs.bucket(fileBucket);
  const tempFilePath = `/tmp/${fileName}`;

  return bucket.file(filePath).download({
    destination: tempFilePath
  }).then(() => {
    console.log('Image downloaded locally to', tempFilePath);
    // Generate a thumbnail using ImageMagick.
    return spawn('convert', [tempFilePath, '-thumbnail', '64x64>', tempFilePath]).then(() => {
      console.log('Thumbnail created at', tempFilePath);
      // We add a 'thumb_' prefix to thumbnails file name. That's where we'll upload the thumbnail.
      const thumbFilePath = filePath.replace(/(\/)?([^\/]*)$/, `$1thumb_$2`);
      // Uploading the thumbnail.
      return bucket.upload(tempFilePath, {
        destination: thumbFilePath
      });
    });
  });
});

Not sure what it means.