Raise your exception like this:
if CONDITION == True:
raise ValueError(HELPING_EXPLANATION)
From PEP 8 — Style Guide for Python Code – Programming Recommendations:
When raising an exception, use raise
ValueError('message')instead of the older formraise ValueError, 'message'.The paren-using form is preferred because when the exception arguments are long or include string formatting, you don’t need to use line continuation characters thanks to the containing parentheses. The older form will be removed in Python 3.