Show the details of an existing firewall rule.

    CLI Example:

    .. code-block:: bash

        salt-cloud -f show_fwrule gce name=allow-http

def show_fwrule(kwargs=None, call=None):
    '''
    Show the details of an existing firewall rule.

    CLI Example:

    .. code-block:: bash

        salt-cloud -f show_fwrule gce name=allow-http
    '''
    if call != 'function':
        raise SaltCloudSystemExit(
            'The show_fwrule function must be called with -f or --function.'
        )
    if not kwargs or 'name' not in kwargs:
        log.error(
            'Must specify name of network.'
        )
        return False

    conn = get_conn()
    return _expand_item(conn.ex_get_firewall(kwargs['name']))