Dear Maintainer, This change from upstream [1] (ignore datetime.datetime.utcfromtimestamp() DeprecationWarning), fixes this issue. I just verified the package builds fine in a sid chroot environment and all tests pass.
Kind Regards https://github.com/ipython/ipykernel/commit/de45c7a4#diff-50c86b7ed8ac2cf95bd48334961bf0530cdc77b5a56f852c5c61b89d735fd711
