Unable to synchronize 'Red Hat Update Infrastructure 3 for RHEL 7 (RPMs) (x86_64)' repository on Red Hat Update Infrastructure 3.

Issue

• Unable to synchronize 'Red Hat Update Infrastructure 3 for RHEL 7 (RPMs) (x86_64)' repository on Red Hat Update Infrastructure 3.
• The sync status is always error.

• In /var/log/messages, 'Not Found' message exists like:

  pulp: celery.worker.strategy:INFO: Received task: pulp.server.managers.repo.sync.sync[4371f8f1-b203-49b7-a608-10e980afeab3]
  pulp: pulp_rpm.plugins.importers.yum.sync:INFO: Downloading metadata from https://cdn.redhat.com/content/dist/rhel/rhui/server/7/7Server/x86_64/rhui/3/os/. <--- HERE
  pulp: celery.worker.strategy:INFO: Received task: pulp.server.async.tasks._release_resource[5a11cc76-38fd-452f-afe2-e0ccc54edb4e]
  pulp: requests.packages.urllib3.connectionpool:INFO: Starting new HTTPS connection (1): cdn.redhat.com
  pulp: celery.worker.job:INFO: Task pulp.server.async.tasks._queue_reserved_task[8a790aa6-32f5-4d7f-b041-64f393687f7a] succeeded in 0.0372013509996s: None
  pulp: requests.packages.urllib3.connectionpool:INFO: Starting new HTTPS connection (1): cdn.redhat.com
  pulp: pulp.server.async.tasks:INFO: Task failed : [4371f8f1-b203-49b7-a608-10e980afeab3] : Error retrieving metadata: Not found
  pulp: celery.worker.job:INFO: Task pulp.server.managers.repo.sync.sync[4371f8f1-b203-49b7-a608-10e980afeab3] raised expected: PulpCodedException()
  

  pulp-admin task details shows

  # pulp-admin -u <username> -p <password> tasks details --task-id 4371f8f1-b203-49b7-a608-10e980afeab3
  +----------------------------------------------------------------------+
                                Task Details
  +----------------------------------------------------------------------+
  
  Operations:       sync
  Resources:        rhel-7-server-rhui-3-rpms-x86_64 (repository)
  State:            Failed
  Start Time:       2017-08-07T04:28:35Z
  Finish Time:      2017-08-07T04:28:38Z
  Result:           N/A
  Task Id:          4371f8f1-b203-49b7-a608-10e980afeab3
  Progress Report:  
    Yum Importer: 
      Comps:            
        State: NOT_STARTED
      Content:          
        Details:       
          Drpm Done:  0
          Drpm Total: 0
          Rpm Done:   0
          Rpm Total:  0
        Error Details: 
        Items Left:    0
        Items Total:   0
        Size Left:     0
        Size Total:    0
        State:         NOT_STARTED
      Distribution:     
        Error Details: 
        Items Left:    0
        Items Total:   0
        State:         NOT_STARTED
      Errata:           
        State: NOT_STARTED
      Metadata:         
        State: NOT_STARTED
      Purge Duplicates: 
        State: NOT_STARTED
  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/repo
                    sitory.py", line 760, in sync     sync_report =
                    sync_repo(transfer_repo, conduit, call_config)   File
                    "/usr/lib/python2.7/site-packages/pulp/server/async/tasks.py",
                    line 658, in wrap_f     return f(*args, **kwargs)   File
                    "/usr/lib/python2.7/site-packages/pulp_rpm/plugins/importers/y
                    um/importer.py", line 81, in sync_repo     report =
                    self._current_sync.run()   File
                    "/usr/lib/python2.7/site-packages/pulp_rpm/plugins/importers/y
                    um/sync.py", line 199, in run     raise
                    PulpCodedException(error_code=error_codes.RPM1004, reason='Not
                    found') PulpCodedException: Error retrieving metadata: Not
                    found