Error in yt-dl filenames served to ffmpeg

[AnExcitedElectron]

When attempting to merge an audio and video file downloaded separately, yt-dl returns an error:

[downloader.ytdl][error] ERROR: ffmpeg: error while loading shared libraries: libslang.so.2: cannot open shared object file: No such file or directory
[downloader.ytdl][debug] Traceback
Traceback (most recent call last):
  File "/snap/gallery-dl/2295/lib/python3.6/site-packages/youtube_dl/YoutubeDL.py", line 2106, in post_process
    files_to_delete, info = pp.run(info)
  File "/snap/gallery-dl/2295/lib/python3.6/site-packages/youtube_dl/postprocessor/ffmpeg.py", line 523, in run
    self.run_ffmpeg_multiple_files(info['__files_to_merge'], temp_filename, args)
  File "/snap/gallery-dl/2295/lib/python3.6/site-packages/youtube_dl/postprocessor/ffmpeg.py", line 235, in run_ffmpeg_multiple_files
    raise FFmpegPostProcessorError(msg)
youtube_dl.postprocessor.ffmpeg.FFmpegPostProcessorError: ffmpeg: error while loading shared libraries: libslang.so.2: cannot open shared object file: No such file or directory

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/snap/gallery-dl/2295/lib/python3.6/site-packages/gallery_dl/downloader/ytdl.py", line 108, in _download_video
    self.ytdl.process_info(info_dict)
  File "/snap/gallery-dl/2295/lib/python3.6/site-packages/youtube_dl/YoutubeDL.py", line 2041, in process_info
    self.post_process(filename, info_dict)
  File "/snap/gallery-dl/2295/lib/python3.6/site-packages/youtube_dl/YoutubeDL.py", line 2108, in post_process
    self.report_error(e.msg)
  File "/snap/gallery-dl/2295/lib/python3.6/site-packages/youtube_dl/YoutubeDL.py", line 628, in report_error
    self.trouble(error_message, tb)
  File "/snap/gallery-dl/2295/lib/python3.6/site-packages/youtube_dl/YoutubeDL.py", line 598, in trouble
    raise DownloadError(message, exc_info)
youtube_dl.utils.DownloadError: ERROR: ffmpeg: error while loading shared libraries: libslang.so.2: cannot open shared object file: No such file or directory

Fresh install of yt-dl, ffmpeg and the gallery-dl snap.
Lubuntu 18.04 OS, but replicable on Ubuntu 16.04.
libslang.so.2 is present.

Error is almost certainly with filenames - files ending in .fdash-AUDIO-1 can't even be played independently.
EDIT: Error does not recur when installing ytdl & gallery-dl with pip.

[mikf]

Fresh install of yt-dl, ffmpeg and the gallery-dl snap.

snap packages don't use your system libraries or programs.

Could you test with the following? Pretty sure this is also going to fail with the same error, although it won't use youtube-dl:

$ gallery-dl -o ugoira=true --ugoira-conv https://danbooru.donmai.us/posts/4507531

[AnExcitedElectron]

Right now I'm having general issues with wifi. Will do when resolved.

[mikf]

@AnExcitedElectron what about #1531 (comment)?

[brlin-tw]

Could you test with the following? Pretty sure this is also going to fail with the same error, although it won't use youtube-dl:

$ gallery-dl -o ugoira=true --ugoira-conv https://danbooru.donmai.us/posts/4507531
[danbooru][warning] netrc: No authentication info
./gallery-dl/danbooru/danbooru_4507531_6b461a5ff53401fa5c1fd50758e3c105.webmffmpeg: error while loading shared libraries: libslang.so.2: cannot open shared object file: No such file or directory

[postprocessor.ugoira][error] Non-zero exit status when running ['ffmpeg', '-f', 'concat', '-i', '/tmp/tmp7ryewq25/ffconcat.txt', '-r', '1000/100', '-c:v', 'libvpx', '-crf', '4', '-b:v', '5000k', '-f', 'webm', '-passlogfile', '/tmp/tmp7ryewq25/ffmpeg2pass', '-pass', '1', '-y', '/dev/null'] (127)
./gallery-dl/danbooru/danbooru_4507531_6b461a5ff53401fa5c1fd50758e3c105.webm

Yes, the issue can also be reproduced, I've made a patch that fixes the problem.

[brlin-tw]

@AnExcitedElectron This issue should no longer be reproduced using the latest build(3403) on the edge channel.

You may install it via running:

sudo snap install --edge gallery-dl

or upgrade it via:

sudo snap refresh --edge gallery-dl

Cheers!