RPM Support

A call to copy content between repositories hits this line which seems like an issue given the package group relation has been dropped from the Package Environment model. https://github.com/pulp/pulp_rpm/blob/master/pulp_rpm/app/tasks/copy.py#L94

for env_package_group in packageenvironment.packagegroups:

Logs:

pulp_tasks:
- pulp_href: "/pulp/api/v3/tasks/be428f2e-20d9-42bb-ac69-741a9e1b15c0/"
  pulp_created: '2020-07-31T01:36:04.455+00:00'
  state: completed
  name: pulp_rpm.app.tasks.copy.copy_content
  started_at: '2020-07-31T01:36:04.670+00:00'
  finished_at: '2020-07-31T01:36:34.115+00:00'
  worker: "/pulp/api/v3/workers/18f81132-6cb9-4ea0-9b49-06a8178bb039/"
  child_tasks: []
  progress_reports: []
  created_resources:
  - "/pulp/api/v3/repositories/rpm/rpm/bba3e5d7-8ca9-4d04-93d9-febbe042c31d/versions/1/"
  reserved_resources_record:
  - "/pulp/api/v3/repositories/rpm/rpm/371a44d3-45a2-43c2-a0c5-850610276de2/"
  - "/pulp/api/v3/repositories/rpm/rpm/bba3e5d7-8ca9-4d04-93d9-febbe042c31d/"
- pulp_href: "/pulp/api/v3/tasks/51cab929-7ddf-4d0f-81ce-dc5f6f92a8a5/"
  pulp_created: '2020-07-31T01:36:04.563+00:00'
  state: failed
  name: pulp_rpm.app.tasks.copy.copy_content
  started_at: '2020-07-31T01:36:34.317+00:00'
  finished_at: '2020-07-31T01:36:34.365+00:00'
  error:
    traceback: |2
        File "/usr/lib/python3.6/site-packages/rq/worker.py", line 883, in perform_job
          rv = job.perform()
        File "/usr/lib/python3.6/site-packages/rq/job.py", line 645, in perform
          self._result = self._execute()
        File "/usr/lib/python3.6/site-packages/rq/job.py", line 651, in _execute
          return self.func(*self.args, **self.kwargs)
        File "/usr/lib64/python3.6/contextlib.py", line 52, in inner
          return func(*args, **kwds)
        File "/usr/lib/python3.6/site-packages/pulp_rpm/app/tasks/copy.py", line 167, in copy_content
          content_to_copy |= find_children_of_content(content_to_copy, source_repo_version)
        File "/usr/lib/python3.6/site-packages/pulp_rpm/app/tasks/copy.py", line 94, in find_children_of_content
          for env_package_group in packageenvironment.packagegroups:
    description: "'PackageEnvironment' object has no attribute 'packagegroups'"
  worker: "/pulp/api/v3/workers/18f81132-6cb9-4ea0-9b49-06a8178bb039/"
  child_tasks: []
  progress_reports: []
  created_resources: []
  reserved_resources_record:
  - "/pulp/api/v3/repositories/rpm/rpm/371a44d3-45a2-43c2-a0c5-850610276de2/"
  - "/pulp/api/v3/repositories/rpm/rpm/bba3e5d7-8ca9-4d04-93d9-febbe042c31d/"
poll_attempts:
  total: 18
  failed: 1