Feature request: Add video license to output dict of Flickr videos

[zhuyifei1999]

(Related ticket for YouTube: #8725)
There is no mentioning of video license in output dict of Flickr videos:

>>> dl.extract_info('https://www.flickr.com/photos/medea_material/3533537450/', download=False).keys()
[Flickr] 3533537450: Downloading api key
[Flickr] 3533537450: Downloading video info
[Flickr] 3533537450: Downloading streams info
[u'display_id', u'extractor', u'protocol', u'description', u'tags', u'timestamp', u'preference', u'uploader', u'duration', u'format_id', u'upload_date', u'id', u'requested_subtitles', u'view_count', u'playlist', u'http_headers', u'title', u'url', u'extractor_key', u'format', u'ext', u'uploader_id', u'comment_count', u'playlist_index', u'webpage_url', u'formats', u'webpage_url_basename']

In a browser, the license in linked to by "Some rights reserved". Ideally, the output should be clear that the license is "Creative Commons Attribution 2.0 Generic" instead of the ambiguous "Some rights reserved".

Why is this needed? It is usually necessary to know the license in order to comply with the terms (see downstream requests).