Add a setting that controls ffmpeg verbosity

Don't display ffmpeg errors in tests

config/config.example.yml

@@ -18,6 +18,9 @@ convert: false
 # Path to your avconv or ffmpeg binary
 avconv: vendor/bin/ffmpeg
 
+# avconv/ffmpeg logging level.
+avconvVerbosity: error
+
 # Path to your rtmpdump binary
 rtmpdump: vendor/bin/rtmpdump
 

config/config_test.yml

@@ -1,2 +1,3 @@
 ---
 convert: false
+avconvVerbosity: fatal

config/config_test_windows.yml

@@ -2,6 +2,7 @@
 convert: false
 python: C:\Python36\python.exe
 avconv: C:\ProgramData\chocolatey\bin\ffmpeg.exe
+avconvVerbosity: fatal
 rtmpdump: C:\ProgramData\chocolatey\bin\rtmpdump
 youtubedl: C:\Python36\Lib\site-packages\youtube_dl\__main__.py
 params: