[cleanup] linter, code formatting and readme

yt_dlp/extractor/common.py

@@ -554,6 +554,8 @@ class InfoExtractor(object):
                     self.initialize()
                     self.write_debug('Extracting URL: %s' % url)
                     ie_result = self._real_extract(url)
+                    if ie_result is None:
+                        return None
                     if self._x_forwarded_for_ip:
                         ie_result['__x_forwarded_for_ip'] = self._x_forwarded_for_ip
                     subtitles = ie_result.get('subtitles')

yt_dlp/extractor/youtube.py

@@ -3636,7 +3636,7 @@ class YoutubeTabIE(YoutubeBaseInfoExtractor):
 
         def get_mobj(url):
             mobj = self._url_re.match(url).groupdict()
-            mobj.update((k, '') for k,v in mobj.items() if v is None)
+            mobj.update((k, '') for k, v in mobj.items() if v is None)
             return mobj
 
         mobj = get_mobj(url)