When a submission is deleted before it's processed in evalmgr:

Traceback (most recent call last):
  File "/vol/sio2/oioioi/oioioi/evalmgr/__init__.py", line 149, in evalmgr_job
  File "/vol/sio2/oioioi/oioioi/evalmgr/__init__.py", line 77, in _run_phase
    kwargs = phase[2].copy()
  File "/vol/sio2/oioioi/oioioi/submitsqueue/handlers.py", line 9, in mark_submission_in_progress
    submission = Submission.objects.get(id=env['submission_id'])
  File "/vol/sio2/venv/local/lib/python2.7/site-packages/django/db/models/manager.py", line 143, in get
    return self.get_query_set().get(*args, **kwargs)
  File "/vol/sio2/venv/local/lib/python2.7/site-packages/django/db/models/query.py", line 404, in get
    self.model._meta.object_name)
DoesNotExist: Submission matching query does not exist.

This ticket should also include writing a test for this case.