Comment 7 for bug 1476779

node roles and network roles mentioned are known in particular env - this is validated CheckBeforeDeploymentTask. There is no sense to validate it when template is being loaded as node roles and network roles set can be changed on the fly.
Same for network_assignments consistency as set of networks is variable.

So, we have to check:
1. Schema
2. Consistency of template (all templates mentioned for node roles are present, templates are not redefined with the same names)