add support for drobox (was: Failed to find file)

[OldAl]

Hi,

Thank you for youtube-dl. Great tool!
Here is an example of failure to access the URL for a cute little video of Galapagos birds. My PC OS is linuxmint-16-KDE , part of ubuntu family, released 22 December. A complete diallog follows:

ak@supremo:~ > youtube-dl --verbose -F https://db.tt/MDom8qsw
[debug] System config: []
[debug] User config: []
[debug] Command-line args: ['--verbose', '-F', 'https://db.tt/MDom8qsw']
[debug] youtube-dl version 2013.08.29
[debug] Python version 2.7.5+ - Linux-3.11.0-12-generic-x86_64-with-LinuxMint-16-petra
[debug] Proxy map: {}
[redirect] Following redirect to https://www.dropbox.com/s/mcnzehi9wo55th4/20131219_085616.mp4
WARNING: Falling back on generic information extractor.
[generic] 20131219_085616.mp4: Downloading webpage
[generic] 20131219_085616.mp4: Extracting information
ERROR: Invalid URL: https://www.dropbox.com/s/mcnzehi9wo55th4/20131219_085616.mp4; please report this issue on https://yt-dl.org/bug . Be sure to call youtube-dl with the --verbose flag and include its complete output. Make sure you are using the latest version; type youtube-dl -U to update.
Traceback (most recent call last):
File "/usr/lib/python2.7/dist-packages/youtube_dl/YoutubeDL.py", line 324, in extract_info
ie_result = ie.extract(url)
File "/usr/lib/python2.7/dist-packages/youtube_dl/extractor/common.py", line 103, in extract
return self._real_extract(url)
File "/usr/lib/python2.7/dist-packages/youtube_dl/extractor/generic.py", line 158, in _real_extract
raise ExtractorError(u'Invalid URL: %s' % url)
ExtractorError: Invalid URL: https://www.dropbox.com/s/mcnzehi9wo55th4/20131219_085616.mp4; please report this issue on https://yt-dl.org/bug . Be sure to call youtube-dl with the --verbose flag and include its complete output. Make sure you are using the latest version; type youtube-dl -U to update.

[1]ak@supremo:~ > youtube-dl -U
It looks like you installed youtube-dl with a package manager, pip, setup.py or a tarball. Please use that to update.
ak@supremo:~ >

[jaimeMF]

We'll have to add support for Dropbox.

[phihag]

I'm on it. It's fairly simple, we just need to download with UA curl/7.

[phihag]

With a current version of youtube-dl, this works just fine. It looks like you installed youtube-dl via pip, so type sudo pip -U youtube-dl to update.