Downloading object to local machine doesn't preserve custom metadata

Downloading a PNG image like below doesn't preserve custom metadata.:

gsutil cp gs://bucket/image.png image.png

I'm using Python and the Pillow library (from PIL.PngImagePlugin import PngInfo) to read the downloaded image and read the metadata which is empty.

Reproduce the issue with the shown gsutil cp command and inspect the downloaded PNG with Pillow's PngImagePlugin. Trace the gsutil download path responsible for object-to-file handling; done means custom metadata present in the source object remains readable from the local PNG.

Written by the indexing model from the issue text.