The R kernel doesn't use base64 padding whereas the Python kernel (via matplotlib) sometimes uses padding. We have to use the `base64` crate's `Indifferent` mode. /cherry-pick v0.161.x Release Notes: - N/A
The R kernel doesn't use base64 padding whereas the Python kernel (via matplotlib) sometimes uses padding. We have to use the `base64` crate's `Indifferent` mode. /cherry-pick v0.161.x Release Notes: - N/A