'Parses the nag file.
Returns:
A NagFile if the file was present else None.'

def _ParseNagFile(self):

    nag_filename = SDKUpdateChecker.MakeNagFilename()
    try:
        fh = open(nag_filename)
    except IOError:
        return None
    try:
        nag = NagFile.Load(fh)
    finally:
        fh.close()
    return nag
