When attempting to change a driver variable name to an "invalid" name, an indicator will now be shown beside the offending variable name. Clicking on this icon will show a popup which provides more information about why the variable name cannot be used. Reasons that it knows about are: 1) Starts with number 2) Has a dot 3) Has a space 4) Starts with or contains a special character 5) Starts with an underscore (Python does allow this, but it's bad practice, and makes checking security of drivers harder) 6) Is a reserved Python keyword