code: func internalRPCError(errStr, context string) *btcjson.RPCError {
  	logStr := errStr
  	if context != "" {
  		logStr = context + ": " + errStr
  	}
  	rpcsLog.Error(logStr)
  	return btcjson.NewRPCError(btcjson.ErrRPCInternal.Code, errStr)
  }
docs: // internalRPCError is a convenience function to convert an internal error to
  // an RPC error with the appropriate code set.  It also logs the error to the
  // RPC server subsystem since internal errors really should not occur.  The
  // context parameter is only used in the log message and may be empty if it's
  // not needed.