We shouldn't check redhat credentials here, take a look at Matthew's [branch](https://github.com/Mirantis/fuelweb/blob/fc8752fe42cfe91b7531d004b84691682a8d39d6/nailgun/nailgun/api/handlers/redhat.py#L66).
In validatos we checks data structure only. In the near future we'll use (maybe next release) jsonschema for this purpose.