Fix a subtle decref bug that caused a GC assertion to fail in a debug build (assert(gc->gc.gc_refs != 0) in visit_decref()).
Fix a subtle decref bug that caused a GC assertion to fail in a debug
build (assert(gc->gc.gc_refs != 0) in visit_decref()).

Because OSSAudioError is a global, we must compensate (twice!) for
PyModule_AddObject()'s "helpful" decref of the object it adds.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator