Not specifyin value for progression in scenario file leads to validation failure

[Sai Sindhur Malleni]

To deploy all agents, the docs suggest to leave the progression field in scenario file empty, however the validation file checks this key only against a enum values of linear, arithmetic, quadratic, geometric. The key isn't checked against type"None". Workaround was to delete the "progression" key from the scenario file.

Leaving the progression field empty leads to

016-04-25 12:20:41.717 19730 ERROR pykwalify.core [-] validation.invalid
2016-04-25 12:20:41.717 19730 ERROR pykwalify.core [-] --- All found errors ---
2016-04-25 12:20:41.717 19730 ERROR pykwalify.core [-] [u"Enum 'None' does not exist. Path: '/execution/progression'", u"Value 'None' is not of type 'str'. Path: '/execution/progression'"]
2016-04-25 12:20:41.718 19730 CRITICAL shaker [-] Exception: File does not conform to schema: <SchemaError: error code 2: Schema validation failed:
 - Enum 'None' does not exist. Path: '/execution/progression'.
 - Value 'None' is not of type 'str'. Path: '/execution/progression'.: Path: '/'>
2016-04-25 12:20:41.718 19730 ERROR shaker Traceback (most recent call last):
2016-04-25 12:20:41.718 19730 ERROR shaker File "/home/stack/shaker-venv/bin/shaker", line 10, in <module>
2016-04-25 12:20:41.718 19730 ERROR shaker sys.exit(main())
2016-04-25 12:20:41.718 19730 ERROR shaker File "/home/stack/shaker-venv/lib/python2.7/site-packages/shaker/engine/server.py", line 265, in main
2016-04-25 12:20:41.718 19730 ERROR shaker act()
2016-04-25 12:20:41.718 19730 ERROR shaker File "/home/stack/shaker-venv/lib/python2.7/site-packages/shaker/engine/server.py", line 235, in act
2016-04-25 12:20:41.718 19730 ERROR shaker utils.validate_yaml(scenario, schema)
2016-04-25 12:20:41.718 19730 ERROR shaker File "/home/stack/shaker-venv/lib/python2.7/site-packages/shaker/engine/utils.py", line 226, in validate_yaml
2016-04-25 12:20:41.718 19730 ERROR shaker raise Exception('File does not conform to schema: %s' % e)
2016-04-25 12:20:41.718 19730 ERROR shaker Exception: File does not conform to schema: <SchemaError: error code 2: Schema validation failed:
2016-04-25 12:20:41.718 19730 ERROR shaker - Enum 'None' does not exist. Path: '/execution/progression'.
2016-04-25 12:20:41.718 19730 ERROR shaker - Value 'None' is not of type 'str'. Path: '/execution/progression'.: Path: '/'>