netconf: Un-helpful error message presented when no service provider is there to handle the RPC call.

This was uncovered during execution of the Core Functionality Tutorials, Chapter 2.

In the tutorial, an RPC call is made to a service provider before that code has been added.

The expected response is:

"error-type": "rpc",
"error-tag": "operation-not-supported",
"error-message": "No implementation for this operation is available."

When this call is made:

curl -H 'Content-Type: application/json' -X POST -d '{"input" : {"toaster:toasterDoneness" : "10","toaster:toasterToastType":"wheat-bread"}}' --verbose -u admin:admin http://localhost:8181/restconf/operations/toaster:make-toast

The response is:

"error-type":"application",
"error-tag":"operation-failed",
"error-message":"The operation encountered an unexpected error while executing."

This error message does not lead the developer to the cause of the error message.

Also, if there's a typo in the URL as follows:

curl -H 'Content-Type: application/json' -X POST -d '{"input" : {"toaster:toasterDoneness" : "10","toaster:toasterToastType":"wheat-bread"}}' --verbose -u admin:admin http://localhost:8181/restconf/operations/toaster:toaster

The error message is:

"error-type":"protocol",
"error-tag":"malformed-message",
"error-message":"Error parsing input: Schema node with name input wasn't found."

"malformed-message" is technically incorrect as the message is valid JSON syntax.