Exception handling in task.py

[kemaleren]

I modified drmaa_wrapper.run_job_using_drmaa() to terminate running jobs when the pipeline gets interrupted:

kemaleren@c41181a

However, the finally block never gets called. It appears that task.pipeline_run() and/or other code in task.py are not handling exceptions correctly, and therefore the ThreadPool workers are not getting gracefully shut down.

I've attached the errors I get when interrupting a run with Ctrl-C: ruffus-stderr.txt