# see https://developers.facebook.com/docs/plugins/embedded-video-player
mobj = re.search(r'''(?x)<div[^>]+
class=(?P<q1>[\'"])[^\'"]*\bfb-video\b[^\'"]*(?P=q1)[^>]+
- data-href=(?P<q2>[\'"])(?P<url>[^\'"]+)(?P=q2)''', webpage)
+ data-href=(?P<q2>[\'"])(?P<url>(?:https?:)?//(?:www\.)?facebook.com/.+?)(?P=q2)''', webpage)
if mobj is not None:
return mobj.group('url')