Can't download worst format from Vimeo

[eradodev]

[debug] System config: []
[debug] User config: []
[debug] Command-line args: [u'--verbose', u'-f', u'worst', u'https://vimeo.com/145571182']
[debug] Encodings: locale UTF-8, fs UTF-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2015.11.13
[debug] Python version 2.7.5 - Linux-3.10.0-123.9.3.el7.x86_64-x86_64-with-centos-7.1.1503-Core
[debug] exe versions: none
[debug] Proxy map: {}
[vimeo] 145571182: Downloading webpage
[vimeo] 145571182: Extracting information
[vimeo] 145571182: Downloading webpage
[vimeo] 145571182: Downloading m3u8 information
[debug] Invoking downloader on u'https://skyfire.vimeocdn.com/1447457309-0x48ebf0c5d46ae61582a0dc3d476d64c39d4eb1ea/145571182/video/439546429/master.m3u8'
[download] Destination: Eresponse-eggo-3-145571182.mp4
ERROR: m3u8 download detected but ffmpeg or avconv could not be found. Please install one.
File "/usr/lib64/python2.7/runpy.py", line 162, in _run_module_as_main
"main", fname, loader, pkg_name)
File "/usr/lib64/python2.7/runpy.py", line 72, in _run_code
exec code in run_globals
File "/var/socialmedia/vimeo/inc/youtube-dl/main.py", line 19, in
youtube_dl.main()
File "/var/socialmedia/vimeo/inc/youtube-dl/youtube_dl/init.py", line 410, in main
_real_main(argv)
File "/var/socialmedia/vimeo/inc/youtube-dl/youtube_dl/init.py", line 400, in _real_main
retcode = ydl.download(all_urls)
File "/var/socialmedia/vimeo/inc/youtube-dl/youtube_dl/YoutubeDL.py", line 1666, in download
url, force_generic_extractor=self.params.get('force_generic_extractor', False))
File "/var/socialmedia/vimeo/inc/youtube-dl/youtube_dl/YoutubeDL.py", line 672, in extract_info
return self.process_ie_result(ie_result, download, extra_info)
File "/var/socialmedia/vimeo/inc/youtube-dl/youtube_dl/YoutubeDL.py", line 718, in process_ie_result
return self.process_video_result(ie_result, download=download)
File "/var/socialmedia/vimeo/inc/youtube-dl/youtube_dl/YoutubeDL.py", line 1336, in process_video_result
self.process_info(new_info)
File "/var/socialmedia/vimeo/inc/youtube-dl/youtube_dl/YoutubeDL.py", line 1598, in process_info
success = dl(filename, info_dict)
File "/var/socialmedia/vimeo/inc/youtube-dl/youtube_dl/YoutubeDL.py", line 1540, in dl
return fd.download(name, info)
File "/var/socialmedia/vimeo/inc/youtube-dl/youtube_dl/downloader/common.py", line 342, in download
return self.real_download(filename, info_dict)
File "/var/socialmedia/vimeo/inc/youtube-dl/youtube_dl/downloader/hls.py", line 27, in real_download
self.report_error('m3u8 download detected but ffmpeg or avconv could not be found. Please install one.')
File "/var/socialmedia/vimeo/inc/youtube-dl/youtube_dl/downloader/common.py", line 155, in report_error
self.ydl.report_error(_args, *_kargs)
File "/var/socialmedia/vimeo/inc/youtube-dl/youtube_dl/YoutubeDL.py", line 536, in report_error
self.trouble(error_message, tb)
File "/var/socialmedia/vimeo/inc/youtube-dl/youtube_dl/YoutubeDL.py", line 498, in trouble
tb_data = traceback.format_list(traceback.extract_stack())

Used to be able to download vimeo videos using worst format tag before #7460 was found and fixed.
Shouldn't this fall to the worst format available instead of forcing a post processor?

[dstftw]

Nominal worst format is generic m3u8 selection URL. For downloading it you must install ffmpeg or avconv as stated in error message.