finish_task_attempt fails with 'NoneType' object is not iterable

[nhammond]

Version 0.7.1rc4

finish_task_attempt fails. Error observed in logs:

[2018-08-30 23:39:08,048: ERROR/MainProcess] Task api.async.finish_task_attempt[1332a508-df0a-437b-a490-dd41d36709f9] raised unexpected: TypeError("'NoneType' object is not iterable",)

From sentence_scoring workflow, split_into_letters step.

[nhammond]

ERROR [2018-08-31 01:41:30,948] Internal Server Error: /api/task-attempts/85bbd077-3f7b-4bcb-88c7-07750ecea4de/finish/ Traceback (most recent call last): File "/Users/s0198839/dev/loom/env/lib/python2.7/site-packages/django/core/handlers/exception.py", line 41, in inner response = get_response(request) File "/Users/s0198839/dev/loom/env/lib/python2.7/site-packages/django/core/handlers/base.py", line 249, in _legacy_get_response response = self._get_response(request) File "/Users/s0198839/dev/loom/env/lib/python2.7/site-packages/django/core/handlers/base.py", line 187, in _get_response response = self.process_exception_by_middleware(e, request) File "/Users/s0198839/dev/loom/env/lib/python2.7/site-packages/django/core/handlers/base.py", line 185, in _get_response response = wrapped_callback(request, *callback_args, **callback_kwargs) File "/Users/s0198839/dev/loom/env/lib/python2.7/site-packages/django/views/decorators/csrf.py", line 58, in wrapped_view return view_func(*args, **kwargs) File "/Users/s0198839/dev/loom/env/lib/python2.7/site-packages/rest_framework/viewsets.py", line 103, in view return self.dispatch(request, *args, **kwargs) File "/Users/s0198839/dev/loom/env/lib/python2.7/site-packages/rest_framework/views.py", line 483, in dispatch response = self.handle_exception(exc) File "/Users/s0198839/dev/loom/env/lib/python2.7/site-packages/rest_framework/views.py", line 443, in handle_exception self.raise_uncaught_exception(exc) File "/Users/s0198839/dev/loom/env/lib/python2.7/site-packages/rest_framework/views.py", line 480, in dispatch response = handler(request, *args, **kwargs) File "/Users/s0198839/dev/loom/loom/server/loomengine_server/api/views.py", line 324, in finish async.execute(async.finish_task_attempt, task_attempt.uuid) File "/Users/s0198839/dev/loom/loom/server/loomengine_server/api/async.py", line 33, in execute return task_function(*args, **kwargs) File "/Users/s0198839/dev/loom/env/lib/python2.7/site-packages/celery/local.py", line 191, in __call__ return self._get_current_object()(*a, **kw) File "/Users/s0198839/dev/loom/env/lib/python2.7/site-packages/celery/app/task.py", line 375, in __call__ return self.run(*args, **kwargs) File "/Users/s0198839/dev/loom/loom/server/loomengine_server/api/async.py", line 218, in finish_task_attempt task_attempt.finish() File "/Users/s0198839/dev/loom/loom/server/loomengine_server/api/models/task_attempts.py", line 119, in finish task.finish() File "/Users/s0198839/dev/loom/loom/server/loomengine_server/api/models/tasks.py", line 208, in finish self._push_all_outputs() File "/Users/s0198839/dev/loom/loom/server/loomengine_server/api/models/tasks.py", line 239, in _push_all_outputs self.run.push_all_outputs() File "/Users/s0198839/dev/loom/loom/server/loomengine_server/api/models/runs.py", line 244, in push_all_outputs run.push_all_inputs() File "/Users/s0198839/dev/loom/loom/server/loomengine_server/api/models/runs.py", line 226, in push_all_inputs = Task.create_unsaved_task_from_input_set(input_set, leaf) TypeError: 'NoneType' object is not iterable ERROR [2018-08-31 01:41:31,070] "POST /api/task-attempts/85bbd077-3f7b-4bcb-88c7-07750ecea4de/finish/ HTTP/1.1" 500 21291

[nhammond]

Fixed in ee57999