mattdrayer/increment-edx-lint: Bump to v0.2.9 and address pylint/pep8 violations

* Fix paver violations to stablize edx-lint update
* Parens, Line2Long
* Fix missing docstrings
* Fix PEP8 issues
* Address PR feedback (thanks @nedbat!)

openedx/core/lib/api/parsers.py

@@ -1,3 +1,6 @@
+"""
+Custom Django REST Framework request/response pipeline parsers
+"""
 from rest_framework import parsers
 
 

openedx/core/lib/api/permissions.py

@@ -1,3 +1,7 @@
+"""
+API library for Django REST Framework permissions-oriented workflows
+"""
+
 from django.conf import settings
 from rest_framework import permissions
 from django.http import Http404
@@ -6,6 +10,9 @@ from student.roles import CourseStaffRole
 
 
 class ApiKeyHeaderPermission(permissions.BasePermission):
+    """
+    Django REST Framework permissions class used to manage API Key integrations
+    """
     def has_permission(self, request, view):
         """
         Check for permissions by matching the configured API key and header

openedx/core/lib/api/view_utils.py

@@ -24,7 +24,6 @@ from openedx.core.lib.api.authentication import (
     OAuth2AuthenticationAllowInactiveUser,
 )
 from openedx.core.lib.api.permissions import IsUserInUrl
-from util.milestones_helpers import any_unfulfilled_milestones
 
 
 class DeveloperErrorViewMixin(object):
@@ -63,6 +62,10 @@ class DeveloperErrorViewMixin(object):
             return self.make_error_response(400, validation_error.messages[0])
 
     def handle_exception(self, exc):
+        """
+        Generalized helper method for managing specific API exception workflows
+        """
+
         if isinstance(exc, APIException):
             return self.make_error_response(exc.status_code, exc.detail)
         elif isinstance(exc, Http404):