Politely notify the user in case of wrong ProductID and VendorID on Mac OS X

[kuz]

In order to run it on Mac one must manually enter the correct ProductID and VendorID values into the code. This update makes it a bit easier by throwing a useful message in the output.

[thiagohersan]

yeah. I'll second this. I was getting IOError exceptions on this line. My fix was to enter VendorID and DeviceID by hand.

Maybe these could be parameters to init along with serial number... ?

[olorin]

Passing to init seems like a sensible idea, but the exception-handling bit of this seems useful also. I'm unable to test as I don't have a Mac; can someone else confirm this works?

[ghost]

I'm fine with passing to init however we should work on a way to add support for the other known headsets as well and find the current one programmatically.
I worked on it but didn't give it much thought since I thought it would return False if no device was found, lack of testing on my part.

Maybe we should add multiple try statements for now?

[thiagohersan]

Could this bit of code from cython-hidapi be used to get vendor/product ID and serial number programmatically?

[ghost]

Yeah I had that commented out. I'm not sure what happened to it.
I just noticed that libusbx also has stable osx support, we could refactor this if that is really the case and use the same code as Windows.

[ghost]

Only took a whole year but I think my latest pull request #154 handles this a bit nicer.