Imgur .gifvs no longer download

[4rm]

Make sure you are using the latest version: run youtube-dl --version and ensure your version is 2018.05.18. If it's not, read this FAQ entry and update. Issues with outdated version will be rejected.

• I've verified and I assure that I'm running youtube-dl 2018.05.18

Before submitting an issue make sure you have:

• At least skimmed through the README, most notably the FAQ and BUGS sections
• Searched the bugtracker for similar issues including closed ones
• Checked that provided video/audio/playlist URLs (if any) are alive and playable in a browser

What is the purpose of your issue?

• Bug report (encountered problems with youtube-dl)
• Site support request (request for adding support for a new site)
• Feature request (request for a new functionality)
• Question
• Other

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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:

C:\Users\Emilio>youtube-dl -v https://i.imgur.com/gTc3gCc.gifv
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: ['-v', 'https://i.imgur.com/gTc3gCc.gifv']
[debug] Encodings: locale cp1252, fs utf-8, out utf-8, pref cp1252
[debug] youtube-dl version 2018.05.18
[debug] Python version 3.6.0 (CPython) - Windows-7-6.1.7601-SP1
[debug] exe versions: ffmpeg N-83585-ga5c1c7a, ffprobe N-83585-ga5c1c7a
[debug] Proxy map: {}
[Imgur] gTc3gCc: Downloading webpage
ERROR: No sources found for video gTc3gCc. Maybe an image?
Traceback (most recent call last):
  File "c:\users\emilio\appdata\local\programs\python\python36\lib\site-packages\youtube_dl\YoutubeDL.py", line 792, in extract_info
    ie_result = ie.extract(url)
  File "c:\users\emilio\appdata\local\programs\python\python36\lib\site-packages\youtube_dl\extractor\common.py", line 503, in extract
    ie_result = self._real_extract(url)
  File "c:\users\emilio\appdata\local\programs\python\python36\lib\site-packages\youtube_dl\extractor\imgur.py", line 67, in _real_extract
    expected=True)
youtube_dl.utils.ExtractorError: No sources found for video gTc3gCc. Maybe an image?

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Description of your issue, suggested solution and other information

youtube-dl isn't seeing the .mp4 inside imgur .gifv's anymore. I think they redesigned some of their site and broke the previous functionality. All that needs to be done I think is replace the extension ".gifv" with ".mp4" and it'll be downloadable.

[yan12125]

Fixed by @jwilk! (#16537)