--exec fails on Windows if the video title has a special character

[richardg867]

• I've verified and I assure that I'm running youtube-dl 2017.06.12
• At least skimmed through README and most notably FAQ and BUGS sections
• Searched the bugtracker for similar issues including closed ones

What is the purpose of your issue?

• Bug report (encountered problems with youtube-dl)

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> youtube-dl -v --exec "ffplay -i {}" http://www.youtube.com/watch?v=9fL5iWgWwno
[debug] System config: []
[debug] User config: []
[debug] Custom config: []
[debug] Command-line args: [u'-v', u'--exec', u'ffplay -i {}', u'http://www.youtube.com/watch?v=9fL5iWgWwno']
[debug] Encodings: locale cp1252, fs mbcs, out cp850, pref cp1252
[debug] youtube-dl version 2017.06.12
[debug] Python version 2.7.13 - Windows-7-6.1.7601-SP1
[debug] exe versions: ffmpeg N-82889-g54931fd, ffprobe N-82889-g54931fd
[debug] Proxy map: {}
[youtube] 9fL5iWgWwno: Downloading webpage
[youtube] 9fL5iWgWwno: Downloading video info webpage
[youtube] 9fL5iWgWwno: Extracting video information
[youtube] {22} signature length 42.43, html5 player vflLxaaub
[youtube] {43} signature length 42.43, html5 player vflLxaaub
[youtube] {18} signature length 42.43, html5 player vflLxaaub
[youtube] {36} signature length 42.43, html5 player vflLxaaub
[youtube] {17} signature length 42.43, html5 player vflLxaaub
[youtube] {137} signature length 42.43, html5 player vflLxaaub
[youtube] {248} signature length 42.43, html5 player vflLxaaub
[youtube] {136} signature length 42.43, html5 player vflLxaaub
[youtube] {247} signature length 42.43, html5 player vflLxaaub
[youtube] {135} signature length 42.43, html5 player vflLxaaub
[youtube] {244} signature length 42.43, html5 player vflLxaaub
[youtube] {134} signature length 42.43, html5 player vflLxaaub
[youtube] {243} signature length 42.43, html5 player vflLxaaub
[youtube] {133} signature length 42.43, html5 player vflLxaaub
[youtube] {242} signature length 42.43, html5 player vflLxaaub
[youtube] {160} signature length 42.43, html5 player vflLxaaub
[youtube] {278} signature length 42.43, html5 player vflLxaaub
[youtube] {140} signature length 42.43, html5 player vflLxaaub
[youtube] {171} signature length 42.43, html5 player vflLxaaub
[youtube] {249} signature length 42.43, html5 player vflLxaaub
[youtube] {250} signature length 42.43, html5 player vflLxaaub
[youtube] {251} signature length 42.43, html5 player vflLxaaub
[youtube] 9fL5iWgWwno: Downloading MPD manifest
WARNING: Requested formats are incompatible for merge and will be merged into mkv.
[debug] Invoking downloader on u'https://r3---sn-oxunxg8pjvn-bpbe.googlevideo.com/videoplayback?id=f5f2f9896816c27a&itag=137&source=youtube&requiressl=yes&initcwndbps=695000&ei=vxJEWY-uG5Ta-AWshqywDg&mv=m&mm=31&ms=au&pl=22&mn=sn-oxunxg8pjvn-bpbe&pcm2cms=yes&ratebypass=yes&mime=video/mp4&gir=yes&clen=97789658&lmt=1458191576575104&dur=188.960&signature=1A628A56E535DB40A69804E97970DA2D95633B72.502A17075C6D14E67FC5CAEACF7EE833DDCF53C6&mt=1497633364&key=dg_yt0&ip=201.37.254.10&ipbits=0&expire=1497655071&sparams=ip,ipbits,expire,id,itag,source,requiressl,initcwndbps,ei,mv,mm,ms,pl,mn,pcm2cms,ratebypass,mime,gir,clen,lmt,dur'
[download] Destination: David Guetta - What I Did For Love (Lyric Video) ft Emeli Sandé-9fL5iWgWwno.f137.mp4
[download] 100% of 93.26MiB in 00:50
[debug] Invoking downloader on u'https://r3---sn-oxunxg8pjvn-bpbe.googlevideo.com/videoplayback?gir=yes&clen=3145355&ms=au&ei=vhJEWa_EMIb2-AXuv6c4&pl=22&mv=m&mt=1497633364&mn=sn-oxunxg8pjvn-bpbe&mm=31&key=yt6&dur=189.009&pcm2cms=yes&source=youtube&id=o-AKYv5fnzuXlB9XGqrge3F0OxpCN51SfotZcmbtNGVyw4&requiressl=yes&lmt=1449649982728386&itag=171&keepalive=yes&ip=201.37.254.10&expire=1497655070&ipbits=0&initcwndbps=695000&sparams=clen%2Cdur%2Cei%2Cgir%2Cid%2Cinitcwndbps%2Cip%2Cipbits%2Citag%2Ckeepalive%2Clmt%2Cmime%2Cmm%2Cmn%2Cms%2Cmv%2Cpcm2cms%2Cpl%2Crequiressl%2Csource%2Cexpire&mime=audio%2Fwebm&signature=DFDA2550667AAFC71BBE95697A16F1EC1E926466.34796726692E7F75E4DCE0EE4132B3A90F3F2525&ratebypass=yes'
[download] Destination: David Guetta - What I Did For Love (Lyric Video) ft Emeli Sandé-9fL5iWgWwno.f171.webm
[download] 100% of 3.00MiB in 00:01
[ffmpeg] Merging formats into "David Guetta - What I Did For Love (Lyric Video) ft Emeli Sandé-9fL5iWgWwno.mkv"
[debug] ffmpeg command line: ffmpeg -y -i 'file:David Guetta - What I Did For Love (Lyric Video) ft Emeli Sandé-9fL5iWgWwno.f137.mp4' -i 'file:David Guetta - What I Did For Love (Lyric Video) ft Emeli Sandé-9fL5iWgWwno.f171.webm' -c copy -map 0:v:0 -map 1:a:0 'file:David Guetta - What I Did For Love (Lyric Video) ft Emeli Sandé-9fL5iWgWwno.temp.mkv'
Deleting original file David Guetta - What I Did For Love (Lyric Video) ft Emeli Sandé-9fL5iWgWwno.f137.mp4 (pass -k to keep)
Deleting original file David Guetta - What I Did For Love (Lyric Video) ft Emeli Sandé-9fL5iWgWwno.f171.webm (pass -k to keep)
[exec] Executing command: ffplay -i 'David Guetta - What I Did For Love (Lyric Video) ft Emeli Sandé-9fL5iWgWwno.mkv'
Traceback (most recent call last):
  File "c:\python27\lib\runpy.py", line 174, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "c:\python27\lib\runpy.py", line 72, in _run_code
    exec code in run_globals
  File "C:\Python27\Scripts\youtube-dl.exe\__main__.py", line 9, in <module>
  File "c:\python27\lib\site-packages\youtube_dl\__init__.py", line 465, in main
    _real_main(argv)
  File "c:\python27\lib\site-packages\youtube_dl\__init__.py", line 455, in _real_main
    retcode = ydl.download(all_urls)
  File "c:\python27\lib\site-packages\youtube_dl\YoutubeDL.py", line 1919, in download
    url, force_generic_extractor=self.params.get('force_generic_extractor', False))
  File "c:\python27\lib\site-packages\youtube_dl\YoutubeDL.py", line 773, in extract_info
    return self.process_ie_result(ie_result, download, extra_info)
  File "c:\python27\lib\site-packages\youtube_dl\YoutubeDL.py", line 827, in process_ie_result
    return self.process_video_result(ie_result, download=download)
  File "c:\python27\lib\site-packages\youtube_dl\YoutubeDL.py", line 1562, in process_video_result
    self.process_info(new_info)
  File "c:\python27\lib\site-packages\youtube_dl\YoutubeDL.py", line 1900, in process_info
    self.post_process(filename, info_dict)
  File "c:\python27\lib\site-packages\youtube_dl\YoutubeDL.py", line 1965, in post_process
    files_to_delete, info = pp.run(info)
  File "c:\python27\lib\site-packages\youtube_dl\postprocessor\execafterdownload.py", line 23, in run
    retCode = subprocess.call(cmd, shell=True)
  File "c:\python27\lib\subprocess.py", line 168, in call
    return Popen(*popenargs, **kwargs).wait()
  File "c:\python27\lib\subprocess.py", line 390, in __init__
    errread, errwrite)
  File "c:\python27\lib\subprocess.py", line 610, in _execute_child
    args = '{} /c "{}"'.format (comspec, args)
UnicodeEncodeError: 'ascii' codec can't encode character u'\xe9' in position 73: ordinal not in range(128)

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Description of your issue, suggested solution and other information

On Windows, the --exec option causes an encoding error if used on videos with special characters in the title (in this case, the offending character is é in David Guetta - What I Did For Love (Lyric Video) ft Emeli Sandé). Note that this issue is not the only blocker for --exec on Windows, see #5889, although a fix for #5889 is not required in order to reproduce this particular issue.

A suggested solution would be encoding the filename according to the detected filesystem encoding. My personal hack-workaround encodes the resulting command in the mbcs encoding which Windows uses, apart from also fixing the quoting issue from #5889.