Repository: youtube-dl
Issue: [safari] Add support for learning paths
Labels: request

## Please follow the guide below

- You will be asked some questions and requested to provide some information, please read them **carefully** and answer honestly
- Put an `x` into all the boxes [ ] relevant to your *issue* (like this: `[x]`)
- Use the *Preview* tab to see what your issue will actually look like

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### Make sure you are using the *latest* version: run `youtube-dl --version` and ensure your version is *2017.08.23*. If it's not, read [this FAQ entry](https://github.com/rg3/youtube-dl/blob/master/README.md#how-do-i-update-youtube-dl) and update. Issues with outdated version will be rejected.
- [x] I've **verified** and **I assure** that I'm running youtube-dl **2017.08.23**

### Before submitting an *issue* make sure you have:
- [x] At least skimmed through the [README](https://github.com/rg3/youtube-dl/blob/master/README.md), **most notably** the [FAQ](https://github.com/rg3/youtube-dl#faq) and [BUGS](https://github.com/rg3/youtube-dl#bugs) sections
- [x] [Searched](https://github.com/rg3/youtube-dl/search?type=Issues) the bugtracker for similar issues including closed ones

### What is the purpose of your *issue*?
- [x] Bug report (encountered problems with youtube-dl)
- [x] Site support request (request for adding support for a new site)
- [ ] Feature request (request for a new functionality)
- [ ] Question
- [ ] Other

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### The following sections concretize particular purposed issues, you can erase any section (the contents between triple ---) not applicable to your *issue*

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Debug log:

```
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: [u'--console-title', u'--restrict-filenames', u'-f', u'mp4[height<=480]', u'--cache-dir', u'/Users/brennebeck/.cache/youtube-dl', u'-o', u'%(autonumber)s-%(title)s.%(ext)s', u'-v', u'--format', u'best', u'https://www.safaribooksonline.com/learning-paths/learning-path-server-side/9781491992289', u'--username=PRIVATE', u'--password=PRIVATE']
[debug] Encodings: locale UTF-8, fs utf-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2017.08.18
[debug] Python version 2.7.12 - Darwin-16.7.0-x86_64-i386-64bit
[debug] exe versions: ffmpeg 3.3.3, ffprobe 3.3.3, rtmpdump 2.4
[debug] Proxy map: {}
[generic] 9781491992289: Requesting header
[redirect] Following redirect to https://www.safaribooksonline.com/learning-paths/learning-path-server-side/9781491992289/
[generic] 9781491992289: Requesting header
WARNING: Falling back on generic information extractor.
[generic] 9781491992289: Downloading webpage
[generic] 9781491992289: Extracting information
ERROR: Unsupported URL: https://www.safaribooksonline.com/learning-paths/learning-path-server-side/9781491992289/
Traceback (most recent call last):
  File "/usr/local/bin/youtube-dl/youtube_dl/extractor/generic.py", line 2103, in _real_extract
    doc = compat_etree_fromstring(webpage.encode('utf-8'))
  File "/usr/local/bin/youtube-dl/youtube_dl/compat.py", line 2539, in compat_etree_fromstring
    doc = _XML(text, parser=etree.XMLParser(target=_TreeBuilder(element_factory=_element_factory)))
  File "/usr/local/bin/youtube-dl/youtube_dl/compat.py", line 2528, in _XML
    parser.feed(text)
  File "/Users/brennebeck/.pyenv/versions/2.7.12/lib/python2.7/xml/etree/ElementTree.py", line 1653, in feed
    self._raiseerror(v)
  File "/Users/brennebeck/.pyenv/versions/2.7.12/lib/python2.7/xml/etree/ElementTree.py", line 1517, in _raiseerror
    raise err
ParseError: not well-formed (invalid token): line 111, column 386
Traceback (most recent call last):
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 776, in extract_info
    ie_result = ie.extract(url)
  File "/usr/local/bin/youtube-dl/youtube_dl/extractor/common.py", line 433, in extract
    ie_result = self._real_extract(url)
  File "/usr/local/bin/youtube-dl/youtube_dl/extractor/generic.py", line 2976, in _real_extract
    raise UnsupportedError(url)
UnsupportedError: Unsupported URL: https://www.safaribooksonline.com/learning-paths/learning-path-server-side/9781491992289/
```

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Unsupported URLs: 
- https//www.safaribooksonline.com/learning-paths/learning-path-server-side/9781491992289/

---

Previously, the 'Learning Paths' in SafariBooksOnline.com would download as a course. Unfortunately, this seems to have stopped working within the last few days (I used this a recently the beginning of the week). I'm not sure what changed that would've broken the compatibility.