Migration Plugin

NoneType' object has no attribute 'cast
    "traceback": "  File \"/usr/lib/python3.6/site-packages/rq/worker.py\", line 936, in perform_job
    rv = job.perform()
  File \"/usr/lib/python3.6/site-packages/rq/job.py\", line 684, in perform
    self._result = self._execute()
  File \"/usr/lib/python3.6/site-packages/rq/job.py\", line 690, in _execute
    return self.func(*self.args, **self.kwargs)
  File \"/usr/lib/python3.6/site-packages/pulp_2to3_migration/app/tasks/migrate.py\", line 136, in migrate_from_pulp2
    pre_migrate_all_without_content(plan, type_to_repo_ids, repo_id_to_type)
  File \"/usr/lib/python3.6/site-packages/pulp_2to3_migration/app/pre_migration.py\", line 384, in pre_migrate_all_without_content
    repo_id, distributors_repos, distributor_migrators, repo)
  File \"/usr/lib/python3.6/site-packages/pulp_2to3_migration/app/pre_migration.py\", line 556, in pre_migrate_distributor
    needs_new_publication = dist_migrator.needs_new_publication(distributor)
  File \"/usr/lib/python3.6/site-packages/pulp_2to3_migration/app/plugin/rpm/repository.py\", line 105, in needs_new_publication
    current_checksum_type = pulp2distributor.pulp3_publication.cast().metadata_checksum_type

from:

https://community.theforeman.org/t/contentmigration-migration-fails-with-error-katello-nonetype-object-has-no-attribute-cast/21828/10