simplify extractor constants

- single strings for URL patterns
- tuples instead of lists for 'directory_fmt' and 'test'
- single-tuple tests where applicable

gallery_dl/extractor/4chan.py

@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
 
-# Copyright 2015-2017 Mike Fährmann
+# Copyright 2015-2019 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
@@ -15,9 +15,9 @@ from .. import text
 class FourchanThreadExtractor(chan.ChanThreadExtractor):
     """Extractor for images from threads from 4chan.org"""
     category = "4chan"
-    pattern = [r"(?:https?://)?boards\.4chan(?:nel)?\.org"
-               r"/([^/]+)/thread/(\d+)"]
-    test = [
+    pattern = (r"(?:https?://)?boards\.4chan(?:nel)?\.org"
+               r"/([^/]+)/thread/(\d+)")
+    test = (
         ("https://boards.4chan.org/tg/thread/15396072/", {
             "url": "39082ad166161966d7ba8e37f2173a824eb540f0",
             "keyword": "7ae2f4049adf0d2f835eb91b6b26b7f4ec882e0a",
@@ -27,7 +27,7 @@ class FourchanThreadExtractor(chan.ChanThreadExtractor):
             "url": "39082ad166161966d7ba8e37f2173a824eb540f0",
             "keyword": "7ae2f4049adf0d2f835eb91b6b26b7f4ec882e0a",
         }),
-    ]
+    )
     api_url = "https://a.4cdn.org/{board}/thread/{thread}.json"
     file_url = "https://i.4cdn.org/{board}/{tim}{ext}"