see #33: update the playbook for python 3.x compatibility

.travis.yml

@@ -1,8 +1,12 @@
 language: python
-python:
-- '2.7'
+matrix:
+  include:
+  - python: '2.7'
+    env: ANSIBLE_VERSION=2.4.6
+  - python: '3.7'
+    env: ANSIBLE_VERSION=2.7.5
 install:
-- pip install ansible==2.4.0
+- pip install ansible==$ANSIBLE_VERSION
 - pip install jmespath
 # Pre-install go-swagger locally since it cannot be fetched from the Travis-CI
 # infrastructures because of rate limits imposed by GitHub on its API.

vars/main.yml

@@ -29,7 +29,7 @@ threescale_cicd_api_version_components: '{{ threescale_cicd_api_version.split(".
 threescale_cicd_api_version_major: '{{ threescale_cicd_api_version_components|first }}'
 threescale_cicd_api_security_requirements: '{{ threescale_cicd_openapi_file_content.security|default([]) }}'
 threescale_cicd_api_security_definitions: '{{ threescale_cicd_openapi_file_content.securityDefinitions|default({}) }}'
-threescale_cicd_api_security_scheme_name: '{{ threescale_cicd_api_security_requirements[0].keys()[0]|default(''none'') }}'
+threescale_cicd_api_security_scheme_name: '{{ (threescale_cicd_api_security_requirements|first|default(''{ "none": {} }'')).keys()|list|first }}'
 threescale_cicd_api_security_scheme: '{{ threescale_cicd_api_security_definitions[threescale_cicd_api_security_scheme_name] if threescale_cicd_api_security_scheme_name in threescale_cicd_api_security_definitions else {} }}'
 threescale_cicd_api_backend_version: '{{ threescale_cicd_backend_version_mapping[threescale_cicd_api_security_scheme.type] }}'
 threescale_cicd_backend_version_mapping: