Wrong error return in BOB_CATCH_MEMBER

Created by: siebenkopf

It appears that for some functions, the error return is -1 and not NULL. Usually, those functions return int and not PyObject*. Particularly, this is the case for the constructors such as: https://github.com/bioidiap/bob.learn.em/blob/master/bob/learn/em/kmeans_trainer.cpp#L119 and for the setter functions such as: https://github.com/bioidiap/bob.learn.em/blob/master/bob/learn/em/kmeans_trainer.cpp#L257

This means that the second value in the BOB_CATCH_MEMBER construct needs to be -1 and not NULL (aka. 0).

@tiagofrepereira2012: could you go through all the files and assure that the error return is correct?