A better test for testing inform_mailing_list function.

improved_test.py

class KeyFileNotFound(IOError):
    
    def __init__(self, key_file_path):
        traceback.print_exc()
        LOG.error("Error: secret key not found. Create it with:")
        if not os.path.isdir(os.path.dirname(key_file_path)):
            print('mkdir -p', os.path.dirname(key_file_path))
        LOG.error('head -c 24 /dev/urandom >', key_file_path)
        sys.exit(1)