Description of problem:
If a sync fails with an Exception, that Exception's traceback is logged (good), and then an Exception like this is logged (bad):

Traceback (most recent call last):
  File "/usr/lib/python2.6/site-packages/celery/app/trace.py", line 240, in trace_task
    R = retval = fun(*args, **kwargs)
  File "/usr/lib/python2.6/site-packages/pulp/server/async/tasks.py", line 306, in __call__
    return super(Task, self).__call__(*args, **kwargs)
  File "/usr/lib/python2.6/site-packages/celery/app/trace.py", line 437, in __protected_call__
    return self.run(*args, **kwargs)
  File "/usr/lib/python2.6/site-packages/pulp/server/tasks/repository.py", line 210, in sync_with_auto_publish
    sync_result = managers.repo_sync_manager().sync(repo_id, sync_config_override=overrides)
  File "/usr/lib/python2.6/site-packages/pulp/server/managers/repo/sync.py", line 113, in sync
    raise PulpExecutionException(_('Importer indicated a failed response'))
PulpExecutionException: Importer indicated a failed response

This traceback isn't useful, and sometimes users will give this to us instead of the real one since it appears "more recently" in the log.

Version-Release number of selected component (if applicable):
2.4.3-1

How reproducible:
Every time

Steps to Reproduce:
1. Edit some code to cause a traceback during a sync
2. Run the sync

Actual results:
You will see two tracebacks in the log, and the latter one is the uninformative one above.

Expected results:
You should see only one traceback in the log.