code: func opcodeDisabled(op *parsedOpcode, vm *Engine) error {
  	str := fmt.Sprintf("attempt to execute disabled opcode %s",
  		op.opcode.name)
  	return scriptError(ErrDisabledOpcode, str)
  }
docs: // *******************************************
  // Opcode implementation functions start here.
  // *******************************************
  // opcodeDisabled is a common handler for disabled opcodes.  It returns an
  // appropriate error indicating the opcode is disabled.  While it would
  // ordinarily make more sense to detect if the script contains any disabled
  // opcodes before executing in an initial parse step, the consensus rules
  // dictate the script doesn't fail until the program counter passes over a
  // disabled opcode (even when they appear in a branch that is not executed).