Given a private key bundle, get the (single) private key

def get_singlesig_privkey(privkey_info, blockchain='bitcoin', **blockchain_opts):
    """
    Given a private key bundle, get the (single) private key
    """
    if blockchain == 'bitcoin':
        return btc_get_singlesig_privkey(privkey_info, **blockchain_opts)
    else:
        raise ValueError('Unknown blockchain "{}"'.format(blockchain))