dependency check

[user9931]

please add some king of dependency check and/or clear log messages instead of tens of error messages that means nothing (like FileNotFoundError: [Errno 2] No such file or directory: 'flac': 'flac' )

[ZivaVatra]

Dependency checking feels more like something that should be handled by your package management system, rather than by flac2all.

However it may be simple to just make the script bomb out if we get a FileNotFoundError. Will have to revisit the logic to remind myself.