Raises is an optional section of Google docstrings. The code on line 455 of docstring.py appears to make it optional, but has a bug, because it is missing a comma after 'raise'. Rather than creating a tuple, it is just unnecessary parenthesis around the string 'raise'. The fix is to add the comma and then raises becomes an optional section and the code works as expected.

In pyment/docstring.py line 455:

 optional_sections=('raise'),

Needs to be changed to:

 optional_sections=('raise',),