Raise exception on error

[CristiFati]

sndinfo returns None when it can't get file info (for whatever reason). That yields an confusing error message like in [SO]: Can't reproduce audio file using python pyo library.

I thought of other possible fixes, but this seemed the best (or simplest):

• Return a tuple containing some invalid data (-1 for numbers and empty stings) - but that would only postpone the error (till when the data will be used)
• Fix (do the None test) all places where this function is used and assume it returns a tuple

After reading the comment did some changes:

• Exception raising is optional and disabled by default
• Enabled it on files from lib. Functionally it makes no difference as an exception would have been raised anyway

Note: There are other places that could be changed (tests, examples) but I don't consider them critical.

[belangeo]

Not sure about this one... Raising an error could break a live performance in a bad way if the user try to load an invalid file (or make a typo in the path). The intended usage here is that the user should always check for None return (like a check for nullptr in C++), and do whatever is the best in its specific setup if the loading of the sound fails.

[belangeo]

Fair enough! Thanks!