Archivers should handle errors during processing of builds

[Caio Begotti]

At least the SSH transport is not handling failures correctly when the Archiver is called. Instead the build reports being successful yet the artifacts were not processed correctly. I think the dependency build status should be updated to FAILURE if that happens. Reporting success when the build ultimately failed doesn't seem right.

[2015-07-24 15:30:27,529: ERROR/MainProcess] Task archives.tasks.process_build_artifacts[9a123c61-f030-4282-866b-f1cbb092b96b] raised unexpected: IOError('Failure',)
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/celery/app/trace.py", line 240, in trace_task
    R = retval = fun(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/celery/app/trace.py", line 437, in __protected_call__
    return self.run(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/archives/tasks.py", line 107, in process_build_artifacts
    rest]).apply()
  File "/usr/lib/python2.7/dist-packages/celery/canvas.py", line 174, in apply
    return self.type.apply(args, kwargs, **options)
  File "/usr/lib/python2.7/dist-packages/celery/app/builtins.py", line 295, in apply
    last and (last.get(), ),
  File "/usr/lib/python2.7/dist-packages/celery/result.py", line 866, in get
    raise self.result
IOError: Failure

I'm simply reporting this bug for the future generations not because I expect to fix it due to the new priorities with Capomastro.