[youtube] save keywords in info jason when --write-info-json is used

youtube_dl/extractor/youtube.py

@@ -1072,6 +1072,9 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
         else:
             video_categories = None
 
+        m = re.findall(r'''<meta(?:\s+[a-zA-Z0-9:._-]+(?:=[a-zA-Z0-9:._-]+|="[^"]+"|='[^']+'))*?\s+property=['"]?og:video:tag['"]?(?:\s+[a-zA-Z0-9:._-]+(?:=[a-zA-Z0-9:._-]+|="[^"]+"|='[^']+'))*?\s+content=['"]?([^>'"]+?)['"]?\s*>'''
+        , video_webpage, re.DOTALL | re.IGNORECASE);
+        video_tags = ", ".join(m)
         # description
         video_description = get_element_by_id("eow-description", video_webpage)
         if video_description:
@@ -1259,6 +1262,7 @@ class YoutubeIE(YoutubeBaseInfoExtractor):
             'title': video_title,
             'thumbnail': video_thumbnail,
             'description': video_description,
+            'tags' : video_tags,
             'categories': video_categories,
             'subtitles': video_subtitles,
             'automatic_captions': automatic_captions,