'index( self, trans, job_id, **kwargs )
* GET /api/jobs/{job_id}/files
Get a file required to staging a job (proper datasets, extra inputs,
task-split inputs, working directory files).
:type   job_id: str
:param  job_id: encoded id string of the job
:type   path: str
:param  path: Path to file.
:type   job_key: str
:param  job_key: A key used to authenticate this request as acting on
behalf or a job runner for the specified job.
..note:
This API method is intended only for consumption by job runners,
not end users.
:rtype:     binary
:returns:   contents of file'

@expose_api_raw_anonymous_and_sessionless
def index(self, trans, job_id, **kwargs):

    self.__authorize_job_access(trans, job_id, **kwargs)
    path = kwargs.get('path', None)
    return open(path, 'rb')
