[*chan] code cleanup

gallery_dl/extractor/4chan.py

@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 
-# Copyright 2015 Mike Fährmann
+# Copyright 2015, 2016 Mike Fährmann
 #
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 2 as
@@ -8,12 +8,11 @@
 
 """Extract images and videos from https://www.4chan.org/"""
 
-from .chan import ChanExtractor
+from . import chan
 
-class FourchanThreadExtractor(ChanExtractor):
+class FourchanThreadExtractor(chan.ChanThreadExtractor):
     """Extractor for images from threads from 4chan.org"""
     category = "4chan"
-    subcategory = "thread"
     pattern = [r"(?:https?://)?boards\.4chan\.org/([^/]+)/thread/(\d+)"]
     test = [("https://boards.4chan.org/tg/thread/15396072/", {
         "url": "39082ad166161966d7ba8e37f2173a824eb540f0",
@@ -22,8 +21,3 @@ class FourchanThreadExtractor(ChanExtractor):
     })]
     api_url = "https://a.4cdn.org/{board}/thread/{thread}.json"
     file_url = "https://i.4cdn.org/{board}/{tim}{ext}"
-
-    def __init__(self, match):
-        ChanExtractor.__init__(
-            self, match.group(1), match.group(2)
-        )