Server swallows validation errors

[mmacaulay]

Validation errors are getting lost in the jayson server. The client sees only an error message indicating that an internal error occurred.

{
  "jsonrpc":"2.0",
  "id":"18dabf6f-f09e-417c-b163-eac85dc94d24",
  "error": {
    "code":-32603,
    "message":"Internal error"
  }
}

To reproduce, call create-user from the console client, setting the email field to test.