add the python_callbacks.so to whl

faiss/python/setup.py

@@ -15,6 +15,7 @@ os.mkdir("faiss")
 shutil.copytree("contrib", "faiss/contrib")
 shutil.copyfile("__init__.py", "faiss/__init__.py")
 shutil.copyfile("loader.py", "faiss/loader.py")
+shutil.copyfile("libfaiss_python_callbacks.so", "faiss/libfaiss_python_callbacks.so")
 
 ext = ".pyd" if platform.system() == 'Windows' else ".so"
 prefix = "Release/" * (platform.system() == 'Windows')