"TypeError: coercing to Unicode: need string or buffer, bool found" if --extract-audio is set for youtube videos

[Obihoernchen]

Issue: Everytime I add "--extract-audio" to postprocess the m4a or mp4 files I get the following error. It doesn't matter which "--audio-format" is set.

Setup:
OS: Mac OS X 10.9 (Mavericks)
ffprobe: 2.3.1 from https://www.evermeet.cx/ffprobe/
youtube-dl: 2014.08.10

Error:
~ # youtube-dl --format bestaudio/best --extract-audio --audio-format mp3 https://www.youtube.com/watch?v=1Ae9SQvAFE4
[youtube] Setting language
[youtube] 1Ae9SQvAFE4: Downloading webpage
[youtube] 1Ae9SQvAFE4: Downloading video info webpage
[youtube] 1Ae9SQvAFE4: Extracting video information
[download] Destination: Fwdslxsh - 4 U (Daktyl Remix) [Trap Music]-SecretlyTrapped.m4a
[download] 100% of 2.87MiB in 00:00
Traceback (most recent call last):
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/runpy.py", line 162, in _run_module_as_main
"main", fname, loader, pkg_name)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/runpy.py", line 72, in _run_code
exec code in run_globals
File "/usr/local/bin/youtube-dl/main.py", line 18, in
File "/usr/local/bin/youtube-dl/youtube_dl/init.py", line 890, in main
File "/usr/local/bin/youtube-dl/youtube_dl/init.py", line 880, in _real_main
File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 1052, in download
File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 527, in extract_info
File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 564, in process_ie_result
File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 830, in process_video_result
File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 1034, in process_info
File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 1086, in post_process
File "/usr/local/bin/youtube-dl/youtube_dl/postprocessor/ffmpeg.py", line 192, in run
TypeError: coercing to Unicode: need string or buffer, bool found

[Obihoernchen]

Shit forgot to install ffmpeg xD (thought it was installed...)

Everything is working fine now. Maybe the check whether ffprobe is available should be extended to check for ffprobe AND ffmpeg.