celery-dyrygent appears to only support python 2.x

[abak]

This is the stack trace i get when attempting to run a workflow. I do not believe it's necessary to include more code, but i can if you think it's necessary.

celery-worker_1    | [2020-04-12 15:11:57,579: INFO/MainProcess] Received task: workflow-processor[e529f4d8-3a0c-4717-af8f-83fd32aaf1dd]
celery-worker_1    | [2020-04-12 15:11:57,609: ERROR/ForkPoolWorker-2] Task workflow-processor[e529f4d8-3a0c-4717-af8f-83fd32aaf1dd] raised unexpected: AttributeError("'dict' object has no attribute 'iteritems'")
celery-worker_1    | Traceback (most recent call last):
celery-worker_1    |   File "/usr/local/lib/python3.7/site-packages/celery/app/trace.py", line 385, in trace_task
celery-worker_1    |     R = retval = fun(*args, **kwargs)
celery-worker_1    |   File "/usr/local/lib/python3.7/site-packages/celery/app/trace.py", line 650, in __protected_call__
celery-worker_1    |     return self.run(*args, **kwargs)
celery-worker_1    |   File "/usr/local/lib/python3.7/site-packages/celery_dyrygent/tasks/processor.py", line 10, in workflow_processor
celery-worker_1    |     wf = Workflow.from_dict(workflow_dict)
celery-worker_1    |   File "/usr/local/lib/python3.7/site-packages/celery_dyrygent/workflows/workflow.py", line 529, in from_dict
celery-worker_1    |     for node_id, node_dict in workflow_dict['nodes'].iteritems()
celery-worker_1    | AttributeError: 'dict' object has no attribute 'iteritems'