Fix Pylint upgrade issues

* Remove unsupported pylint disable options
    * star-args removed in Pylint 1.4.3
    * abstract-class-little-used removed in Pylint 1.4.3

* Fixes new lint errors

* Copy dummy-variable-rgx expression to new ignored-argument-names expression to ignore unused funtion arguments

* Notable changes
    * Refactor to satisfy Pylint no-else-return warning
    * Fix Pylint inconsistent-return-statements warning
    * Refactor to satisfy consider-iterating-dictionary
    * Remove methods with only super call to satisfy useless-super-delegation
    * Refactor too-many-nested-statements where possible
    * Suppress type checked errors where member is dynamically added (notably derived from josepy.JSONObjectWithFields)
    * Remove None default of func parameter for ExitHandler and ErrorHandler

Resolves #5973

letshelp-certbot/letshelp_certbot/apache_test.py

@@ -2,11 +2,11 @@
 import argparse
 import functools
 import os
-import pkg_resources
 import subprocess
 import tarfile
 import tempfile
 import unittest
+import pkg_resources
 
 import mock
 # six is used in mock.patch()