Remove the key from the cache bank with all the key content.

def flush(bank, key=None):
    '''
    Remove the key from the cache bank with all the key content.
    '''
    if key is None:
        c_key = bank
    else:
        c_key = '{0}/{1}'.format(bank, key)
    try:
        return api.kv.delete(c_key, recurse=key is None)
    except Exception as exc:
        raise SaltCacheError(
            'There was an error removing the key, {0}: {1}'.format(
                c_key, exc
            )
        )