fix unmarshal errors not found for known k8s schema

[fedeztk]

Description

Fixes #523 (known schema not raising errors when incompatible with k8s resource definitions)

Type of change

• [x] Bug fix :bug:
• [ ] New feature :sparkles:
• [ ] This change requires a documentation update :book:
• [ ] Breaking changes :warning:

  How Has This Been Tested?

Tested using the example provided in #523. Prior to this change there was no error; now, known resources (e.g. Deployments) raise an error when the unmarshaling goes wrong (like unquoted labels) and clearly shows that there is a misconfiguration in the manifest.

Checklist:

• [x] I have :tophat: my changes (A 🎩 specifically includes pulling down changes, setting them up, and manually testing the changed features and potential side effects to make sure nothing is broken)
• [x] I have performed a self-review of my own code
• [ ] I have made corresponding changes to the documentation
• [ ] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] The test coverage did not decrease
• [x] I have signed the appropriate Contributor License Agreement