Ubuntu 16.04 repo issue

I am trying to add Ubuntu-16.04 repository in katello while syncing getting following error.
Kindly help to fix this issue.

Nov 29 05:16:58 foreman.internal.net pulp[23670]: celery.app.trace:ERROR: [0a8d4804] (23670-91552) IOError: [Errno 2] No such file or directory: u'/var/cache/pulp/reserved_resource_worker-1@foreman.internal.net/0a8d4804-031a-473d-a684-38bf99fc594f/packages/7f/9f/gtk-sharp2-examples_2.12.10-6_all.deb'

Which ubuntu repository are you using?
Which katello / pulp versions ?
Can you please verify, that the package exists in the repository?

Hello Bernhard,

Ubuntu Repo: http://archive.ubuntu.com/
Version: xenial / Main
Pulp Version: 2.20
Katello Version: 1.22
Not sure this package is available on this repo.