Issue 6945 - Add script to make filter list diffs

tests/test_diff_script.py

 # This file is part of Adblock Plus <https://adblockplus.org/>,
 # Copyright (C) 2006-present eyeo GmbH
 #
 # Adblock Plus is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 3 as
 # published by the Free Software Foundation.
 #
 # Adblock Plus is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU General Public License
 # along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
 
-"""Functional tests for the rendering script.
-
-These tests create files on the filesystem, bring up a small webserver and
-generally test the script under reasonably realistic conditions.
-"""
+"""Functional tests for the diff script."""
 
 from __future__ import unicode_literals
 
 import pytest
 import subprocess
 import io
 
 from test_differ import BASE, LATEST
 
 
@@ skipping 49 matching lines @@
 def test_no_latest_file(rootdir):
     code, err, _ = run_script(str(rootdir.join('base.txt')), 'wrong.txt')
     assert code == 1
     assert 'No such file or directory' in err
 
 
 def test_diff_to_self(rootdir):
     _, _, out = run_script(str(rootdir.join('latest.txt')),
                            str(rootdir.join('latest.txt')))
     assert out == '[Adblock Plus Diff]\n'