pyccc: error state handling

[avirshup]

pyccc (both 0.6.5 and dev) reports that a job with status "failed" is "finished", and then throws an unrelated error when trying to get the job's results. It SHOULD report an error state, and ideally include CCC's error message.

To reproduce (fails because image does not exist):

engine = pyccc.CloudComputeCannon("cloudcomputecannon.bionano.autodesk.com:9000")
job = engine.launch("image_does_not_exist", 'echo hello')