Improvement: Use voluptuous library for data validation

[Devdatta Kulkarni]

Voluptuous is a package for data validation (https://pypi.python.org/pypi/voluptuous/)

It is used by Zuul (https://github.com/openstack-infra/zuul/blob/master/requirements.txt)
It supports schema-based declarative approach for validating input data.
Solum will benefit from using this.

devdatta-kulkarni started on that path here:
https://review.openstack.org/#/c/77251/

But, gates won't pass this patch because voluptuous is not part of openstack/requirements. So abandoning this patch for now. Once we get voluptuous merged into openstack/requirements we can revisit this.

Here are some relevant links:

How to propose new addition to OpenStack/Requirements:
https://wiki.openstack.org/wiki/Requirements

Current openstack/requirements:
https://github.com/openstack/requirements/blob/master/global-requirements.txt

Related Blueprint: https://blueprints.launchpad.net/solum/+spec/solum-input-validation

[Angus Salkeld (asalkeld)]

I am not sure of the extra value it will give us over wsme objects. It would be good to quantify this and make sure it does in fact add a tangible benefit.