Can't download audio from Rai Media

[xoich]

• I've verified and I assure that I'm running youtube-dl 2017.08.23
• At least skimmed through the README, most notably the FAQ and BUGS sections
• Searched the bugtracker for similar issues including closed ones

What is the purpose of your issue?

• Bug report (encountered problems with youtube-dl)

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Log

$ youtube-dl -v "http://www.seigradi.rai.it/dl/portaleRadio/media/ContentItem-9dba3e55-bfe6-417d-ac25-afbf81327f99.html"
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: [u'-v', u'http://www.seigradi.rai.it/dl/portaleRadio/media/ContentItem-9dba3e55-bfe6-417d-ac25-afbf81327f99.html']
[debug] Encodings: locale UTF-8, fs UTF-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2017.08.23
[debug] Python version 2.7.13 - Linux-4.9.0-3-amd64-x86_64-with-debian-9.1
[debug] exe versions: ffmpeg 3.2.5-1, ffprobe 3.2.5-1, rtmpdump 2.4
[debug] Proxy map: {}
[Rai] 9dba3e55-bfe6-417d-ac25-afbf81327f99: Downloading webpage
[Rai] 9dba3e55-bfe6-417d-ac25-afbf81327f99: Downloading video JSON
Traceback (most recent call last):
  File "/home/daniele/.local/bin/youtube-dl", line 11, in <module>
    sys.exit(main())
  File "/home/daniele/.local/lib/python2.7/site-packages/youtube_dl/__init__.py", line 465, in main
    _real_main(argv)
  File "/home/daniele/.local/lib/python2.7/site-packages/youtube_dl/__init__.py", line 455, in _real_main
    retcode = ydl.download(all_urls)
  File "/home/daniele/.local/lib/python2.7/site-packages/youtube_dl/YoutubeDL.py", line 1958, in download
    url, force_generic_extractor=self.params.get('force_generic_extractor', False))
  File "/home/daniele/.local/lib/python2.7/site-packages/youtube_dl/YoutubeDL.py", line 776, in extract_info
    ie_result = ie.extract(url)
  File "/home/daniele/.local/lib/python2.7/site-packages/youtube_dl/extractor/common.py", line 434, in extract
    ie_result = self._real_extract(url)
  File "/home/daniele/.local/lib/python2.7/site-packages/youtube_dl/extractor/rai.py", line 421, in _real_extract
    return self._extract_from_content_id(content_item_id, url)
  File "/home/daniele/.local/lib/python2.7/site-packages/youtube_dl/extractor/rai.py", line 359, in _extract_from_content_id
    self._sort_formats(relinker_info['formats'])
  File "/home/daniele/.local/lib/python2.7/site-packages/youtube_dl/extractor/common.py", line 1077, in _sort_formats
    if 'tbr' not in f and f.get('abr') is not None and f.get('vbr') is not None:
AttributeError: 'unicode' object has no attribute 'get'

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Downloading Rai media content is supported and used to work in the past (I tried the radio podcast), but it doesn't anymore.