There is another request open for exactly the same issue:
https://community.theforeman.org/t/smart-proxy-synchronize-always-fails-at-the-same-repository/21371
If you search through /v/l/m on the smart proxy server, you will find a python backtrace at the time of the error. In my case it is always during “pulp: pulp_rpm.plugins.importers.yum.purge:INFO: [fa7ed02d] Removing missing units”
The backtrace looks like this:
Dec 4 14:28:44 smartproxy pulp: pulp_rpm.plugins.importers.yum.sync:ERROR: [fa7ed02d] (3958-15456) 'NoneType' object has no attribute 'findall'
Dec 4 14:28:44 smartproxy pulp: pulp_rpm.plugins.importers.yum.sync:ERROR: [fa7ed02d] (3958-15456) Traceback (most recent call last):
Dec 4 14:28:44 smartproxy pulp: pulp_rpm.plugins.importers.yum.sync:ERROR: [fa7ed02d] (3958-15456) File "/usr/lib/python2.7/site-packages/pulp_rpm/plugins/importers/yum/sync.py", line 294, in run
Dec 4 14:28:44 smartproxy pulp: pulp_rpm.plugins.importers.yum.sync:ERROR: [fa7ed02d] (3958-15456) self.update_content(metadata_files, url)
Dec 4 14:28:44 smartproxy pulp: pulp_rpm.plugins.importers.yum.sync:ERROR: [fa7ed02d] (3958-15456) File "/usr/lib/python2.7/site-packages/pulp_rpm/plugins/importers/yum/sync.py", line 627, in update_content
Dec 4 14:28:44 smartproxy pulp: pulp_rpm.plugins.importers.yum.sync:ERROR: [fa7ed02d] (3958-15456) purge.purge_unwanted_units(metadata_files, self.conduit, self.config, catalog)
Dec 4 14:28:44 smartproxy pulp: pulp_rpm.plugins.importers.yum.sync:ERROR: [fa7ed02d] (3958-15456) File "/usr/lib/python2.7/site-packages/pulp_rpm/plugins/importers/yum/purge.py", line 46, in purge_unwanted_units
Dec 4 14:28:44 smartproxy pulp: pulp_rpm.plugins.importers.yum.sync:ERROR: [fa7ed02d] (3958-15456) remove_missing_groups(metadata_files, conduit)
Dec 4 14:28:44 smartproxy pulp: pulp_rpm.plugins.importers.yum.sync:ERROR: [fa7ed02d] (3958-15456) File "/usr/lib/python2.7/site-packages/pulp_rpm/plugins/importers/yum/purge.py", line 165, in remove_missing_groups
Dec 4 14:28:44 smartproxy pulp: pulp_rpm.plugins.importers.yum.sync:ERROR: [fa7ed02d] (3958-15456) remote_named_tuples = get_remote_units(file_function, group.GROUP_TAG, process_func)
Dec 4 14:28:44 smartproxy pulp: pulp_rpm.plugins.importers.yum.sync:ERROR: [fa7ed02d] (3958-15456) File "/usr/lib/python2.7/site-packages/pulp_rpm/plugins/importers/yum/purge.py", line 277, in get_remote_units
Dec 4 14:28:44 smartproxy pulp: pulp_rpm.plugins.importers.yum.sync:ERROR: [fa7ed02d] (3958-15456) for unit in package_info_generator:
Dec 4 14:28:44 smartproxy pulp: pulp_rpm.plugins.importers.yum.sync:ERROR: [fa7ed02d] (3958-15456) File "/usr/lib/python2.7/site-packages/pulp_rpm/plugins/importers/yum/repomd/packages.py", line 64, in package_list_generator
Dec 4 14:28:44 smartproxy pulp: pulp_rpm.plugins.importers.yum.sync:ERROR: [fa7ed02d] (3958-15456) package_info = process_func(element)
Dec 4 14:28:44 smartproxy pulp: pulp_rpm.plugins.importers.yum.sync:ERROR: [fa7ed02d] (3958-15456) File "/usr/lib/python2.7/site-packages/pulp_rpm/plugins/importers/yum/repomd/group.py", line 32, in process_group_element
Dec 4 14:28:44 smartproxy pulp: pulp_rpm.plugins.importers.yum.sync:ERROR: [fa7ed02d] (3958-15456) packagelist.findall('packagereq'))
Dec 4 14:28:44 smartproxy pulp: pulp_rpm.plugins.importers.yum.sync:ERROR: [fa7ed02d] (3958-15456) AttributeError: 'NoneType' object has no attribute 'findall'
Dec 4 14:28:44 smartproxy pulp: pulp.server.async.tasks:INFO: [fa7ed02d] Task failed : [fa7ed02d-03de-45dd-96e0-4f74e20c386c]
Dec 4 14:28:44 smartproxy pulp: celery.app.trace:ERROR: [fa7ed02d] (3958-15456) Task pulp.server.managers.repo.sync.sync[fa7ed02d-03de-45dd-96e0-4f74e20c386c] raised unexpected: PulpExecutionException('Importer indicated a failed response',)
Dec 4 14:28:44 smartproxy pulp: celery.app.trace:ERROR: [fa7ed02d] (3958-15456) Traceback (most recent call last):
Dec 4 14:28:44 smartproxy pulp: celery.app.trace:ERROR: [fa7ed02d] (3958-15456) File "/usr/lib/python2.7/site-packages/celery/app/trace.py", line 367, in trace_task
Dec 4 14:28:44 smartproxy pulp: celery.app.trace:ERROR: [fa7ed02d] (3958-15456) R = retval = fun(*args, **kwargs)
Dec 4 14:28:44 smartproxy pulp: celery.app.trace:ERROR: [fa7ed02d] (3958-15456) File "/usr/lib/python2.7/site-packages/pulp/server/async/tasks.py", line 688, in __call__
Dec 4 14:28:44 smartproxy pulp: celery.app.trace:ERROR: [fa7ed02d] (3958-15456) return super(Task, self).__call__(*args, **kwargs)
Dec 4 14:28:44 smartproxy pulp: celery.app.trace:ERROR: [fa7ed02d] (3958-15456) File "/usr/lib/python2.7/site-packages/pulp/server/async/tasks.py", line 110, in __call__
Dec 4 14:28:44 smartproxy pulp: celery.app.trace:ERROR: [fa7ed02d] (3958-15456) return super(PulpTask, self).__call__(*args, **kwargs)
Dec 4 14:28:44 smartproxy pulp: celery.app.trace:ERROR: [fa7ed02d] (3958-15456) File "/usr/lib/python2.7/site-packages/celery/app/trace.py", line 622, in __protected_call__
Dec 4 14:28:44 smartproxy pulp: celery.app.trace:ERROR: [fa7ed02d] (3958-15456) return self.run(*args, **kwargs)
Dec 4 14:28:44 smartproxy pulp: celery.app.trace:ERROR: [fa7ed02d] (3958-15456) File "/usr/lib/python2.7/site-packages/pulp/server/controllers/repository.py", line 854, in sync
Dec 4 14:28:44 smartproxy pulp: celery.app.trace:ERROR: [fa7ed02d] (3958-15456) raise pulp_exceptions.PulpExecutionException(_('Importer indicated a failed response'))
Dec 4 14:28:44 smartproxy pulp: celery.app.trace:ERROR: [fa7ed02d] (3958-15456) PulpExecutionException: Importer indicated a failed response
Which leads to the PLP0000 error. You should see above the back trace which repository it tried to sync. In my case its always failing at CentOS 7 and CentOS 8 AppStream.