Add Support for NFL Gamepass

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

Make sure you are using the latest version: run `youtube-dl --version` and ensure your version is 2017.12.10. If it's not, read this FAQ entry and update. Issues with outdated version will be rejected.

[x] I've verified and I assure that I'm running youtube-dl 2017.12.10

Before submitting an issue make sure you have:

[x] At least skimmed through the README, most notably the FAQ and BUGS sections
[x] Searched the bugtracker for similar issues including closed ones

What is the purpose of your issue?

[ ] 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

If the purpose of this issue is a bug report, site support request or you are not completely sure provide the full verbose output as follows:

Add the -v flag to your command line you run youtube-dl with (youtube-dl -v <your command line>), copy the whole output and insert it here. It should look similar to one below (replace it with your log inserted between triple ```):

$ youtube-dl --cookies cookies.txt -v -F https://gamepass.nfl.com/game/colts-at-bills-on-12102017
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: [u'--cookies', u'/Users/maxyellen/Downloads/cookies.txt', u'-v', u'-F', u'https://gamepass.nfl.com/game/colts-at-bills-on-12102017']
[debug] Encodings: locale UTF-8, fs utf-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2017.12.10
[debug] Python version 2.7.10 - Darwin-17.2.0-x86_64-i386-64bit
[debug] exe versions: ffmpeg 3.4.1, ffprobe 3.4.1
[debug] Proxy map: {}
[generic] colts-at-bills-on-12102017: Requesting header
WARNING: Falling back on generic information extractor.
[generic] colts-at-bills-on-12102017: Downloading webpage
[generic] colts-at-bills-on-12102017: Extracting information
ERROR: Unsupported URL: https://gamepass.nfl.com/game/colts-at-bills-on-12102017
Traceback (most recent call last):
  File "/usr/local/bin/youtube-dl/youtube_dl/extractor/generic.py", line 2163, 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 "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/xml/etree/ElementTree.py", line 1642, in feed
    self._raiseerror(v)
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/xml/etree/ElementTree.py", line 1506, in _raiseerror
    raise err
ParseError: not well-formed (invalid token): line 147, column 31
Traceback (most recent call last):
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 784, in extract_info
    ie_result = ie.extract(url)
  File "/usr/local/bin/youtube-dl/youtube_dl/extractor/common.py", line 437, in extract
    ie_result = self._real_extract(url)
  File "/usr/local/bin/youtube-dl/youtube_dl/extractor/generic.py", line 3063, in _real_extract
    raise UnsupportedError(url)
UnsupportedError: Unsupported URL: https://gamepass.nfl.com/game/colts-at-bills-on-12102017

If the purpose of this issue is a site support request please provide all kinds of example URLs support for which should be included (replace following example URLs by yours):

Single video: https://gamepass.nfl.com/game/colts-at-bills-on-12102017
Single video: https://gamepass.nfl.com/game/vikings-at-panthers-on-12102017?condensed=true

Note that youtube-dl does not support sites dedicated to copyright infringement. In order for site support request to be accepted all provided example URLs should not violate any copyrights.

Description of your issue, suggested solution and other information

You need a login to access nfl gamepass. I can provide a cookies.txt file, but I don't want to post it publicly. I can email it to you.

ytdl-org / youtube-dl