class TextBoxDrawerError(Exception):
    pass

class MissingSVGFile(TextBoxDrawerError):
    pass

class TextBoxNotFoundInSVG(TextBoxDrawerError):
    pass

class MissingSVGViewBox(TextBoxDrawerError):
    pass

Add custom exceptions for TextBoxDrawer
Add custom exceptions for TextBoxDrawer

This is a skeleton for now, with docstrings etc. to follow
