Retrieve a key from the hiera store

    :param password_name: Name of the key to retrieve
    :type  password_name: type

def get_hiera_key(key_name):
    """Retrieve a key from the hiera store

    :param password_name: Name of the key to retrieve
    :type  password_name: type

    """
    command = ["hiera", key_name]
    p = subprocess.Popen(command, stdout=subprocess.PIPE)
    out, err = p.communicate()
    return out