Problem Statement

$ python scripts/add_attribute.py Permissions triage bool
Traceback (most recent call last):
  File "<...>\PyGithub\scripts\add_attribute.py", line 124, in <module>
    line = lines[i].rstrip()
IndexError: list index out of range

--> Adding a new attribute at the end of the existing list of attributes in class Permissions fails.
--> In this case the last attribute name was "push", so "triage" comes last.

Solution Approach

In case the new attribute name will result in adding it at the end of the list of attributes, then the processing within the script at https://github.com/PyGithub/PyGithub/blob/master/scripts/add_attribute.py#L89 was already processing the next source code line which already contains the _initAttributes function.
Subsequently at https://github.com/PyGithub/PyGithub/blob/master/scripts/add_attribute.py#L122 inInit is set to False, but only checked again after reading already the next line. This means the following code block will never again notice the place of the _initAttributes and fails at the end of the file due to endless loop.

Problem can be fixed by conditionally remembering we already reached the _initAttributes function, so replace:

with

inInit = True if line == "    def _initAttributes(self):" else False