When deviation is applied on certain yang node it should be marked as not-supported and on restconf API HTTP error code 501 (not-implemented) should be returned.
RFC 7950 does not clearly defines what the effect of deviations should be.
I agree it sounds like a good idea to return not implemented, I mark it as enhancement request.
When deviation is applied on certain yang node it should be marked as not-supported and on restconf API HTTP error code 501 (not-implemented) should be returned.