Why do repository synchronization tasks fail in Satellite 6 with "Importer indicated a failed response" and "command document too large"?

Issue

• Why do repository synchronization tasks fail in Satellite 6 with Importer indicated a failed response and command document too large?

• Inspecting the Dynflow console for the task shows the following details:

85: Actions::Pulp::Consumer::SyncCapsule (skipped) [ 2600.20s / 55.35s ]
Started at: 2017-07-20 12:09:03 UTC
Ended at: 2017-07-20 12:52:23 UTC
Real time: 2600.20s
Execution time (excluding suspended state): 55.35s

Input:

---
capsule_id: 8
repo_pulp_id: ORG-Library-HA_RHEL7_x86_64-Red_Hat_Software_Collections__for_RHEL_Server_-Red_Hat_Software_Collections_RPMs_for_Red_Hat_Enterprise_Linux_7_Server_x86_64_7Server
remote_user: admin
remote_cp_user: admin
locale: en

Output:

---
pulp_tasks:
- exception: 
  task_type: pulp.server.managers.repo.sync.sync
  _href: "/pulp/api/v2/tasks/caa86789-46a2-4c15-8755-1e3093fb6ac1/"
  task_id: caa86789-46a2-4c15-8755-1e3093fb6ac1
  tags:
  - pulp:repository:ORG-Library-HA_RHEL7_x86_64-Red_Hat_Software_Collections__for_RHEL_Server_-Red_Hat_Software_Collections_RPMs_for_Red_Hat_Enterprise_Linux_7_Server_x86_64_7Server
  - pulp:action:sync
  finish_time: '2017-07-20T12:21:27Z'
  _ns: task_status
  start_time: '2017-07-20T12:12:18Z'
  traceback: |
    Traceback (most recent call last):
      File "/usr/lib/python2.7/site-packages/celery/app/trace.py", line 240, in trace_task
        R = retval = fun(*args, **kwargs)
      File "/usr/lib/python2.7/site-packages/pulp/server/async/tasks.py", line 473, in __call__
        return super(Task, self).__call__(*args, **kwargs)
      File "/usr/lib/python2.7/site-packages/pulp/server/async/tasks.py", line 103, in __call__
        return super(PulpTask, self).__call__(*args, **kwargs)
      File "/usr/lib/python2.7/site-packages/celery/app/trace.py", line 437, in __protected_call__
        return self.run(*args, **kwargs)
      File "/usr/lib/python2.7/site-packages/pulp/server/controllers/repository.py", line 812, in sync
        raise pulp_exceptions.PulpExecutionException(_('Importer indicated a failed response'))
    PulpExecutionException: Importer indicated a failed response

  spawned_tasks: []
  progress_report:  
[...]
      errata:
        state: FAILED
        error: command document too large
[...]