asd.py

import os
import shutil

rootDir = 'G:/testasd/'

print('[',rootDir,']')
for (dirPath, dirNames, fileNames) in os.walk(rootDir):
    for file in fileNames:
        root, ext = os.path.splitext(file)
        if ext not in ('.mp3', '.flac', '.m4a'):
            src = os.path.join(dirPath, file)
            dest = os.path.join(dirPath, file + '.mp3')

            ok = True
            try:
                shutil.move(src,dest)
            except Exception:
                ok = False

            print("{0:40} => {1:40} [{2}]".format(os.path.relpath(src, rootDir), os.path.relpath(dest, rootDir), 'OK' if ok else 'ERROR'))