DeprecationWarning on Python 3.6

We get the following warnings using the `drmaa` module:
```
  /opt/anaconda/lib/python3.6/site-packages/drmaa/session.py:340: DeprecationWarning: generator 'run_bulk_job' raised StopIteration
    return list(run_bulk_job(jobTemplate, beginIndex, endIndex, step))
```
