rpc: add custom errors to sendrawtransaction

In case of unsuccessful relyReason sendRawTransaction should return
errors with codes [-500, ..., -505] instead of error with code -32603

pkg/rpc/server/server.go

@@ -854,28 +854,24 @@ func (s *Server) sendrawtransaction(reqParams request.Params) (interface{}, erro
 		tx := &transaction.Transaction{}
 		tx.DecodeBinary(r)
 		if r.Err != nil {
-			err = errors.Wrap(r.Err, "transaction DecodeBinary failed")
+			return nil, response.ErrInvalidParams
-		} else {
+		}
 		relayReason := s.coreServer.RelayTxn(tx)
 		switch relayReason {
 		case network.RelaySucceed:
 			results = true
 		case network.RelayAlreadyExists:
-				err = errors.New("block or transaction already exists and cannot be sent repeatedly")
+			resultsErr = response.ErrAlreadyExists
 		case network.RelayOutOfMemory:
-				err = errors.New("the memory pool is full and no more transactions can be sent")
+			resultsErr = response.ErrOutOfMemory
 		case network.RelayUnableToVerify:
-				err = errors.New("the block cannot be validated")
+			resultsErr = response.ErrUnableToVerify
 		case network.RelayInvalid:
-				err = errors.New("block or transaction validation failed")
+			resultsErr = response.ErrValidationFailed
 		case network.RelayPolicyFail:
-				err = errors.New("one of the Policy filters failed")
+			resultsErr = response.ErrPolicyFail
 		default:
-				err = errors.New("unknown error")
+			resultsErr = response.ErrUnknown
-			}
-		}
-		if err != nil {
-			resultsErr = response.NewInternalServerError(err.Error(), err)
 		}
 	}