Role crush when running ansible with python3

Python3 does not have iteritems method on dict type.

roles/docker/vars/main.yml:  {%- for _key,_value in (docker_service_environment_variables | default({})).iteritems() %}
roles/docker/tasks/network/create.yml:    {% for option_name, option_value in docker_network_options.iteritems() %}

we should use method items instead