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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def __firewall_cmd(cmd):
    '''
    Return the firewall-cmd location
    '''
    firewall_cmd = '{0} {1}'.format(salt.utils.path.which('firewall-cmd'), cmd)
    out = __salt__['cmd.run_all'](firewall_cmd)

    if out['retcode'] != 0:
        if not out['stderr']:
            msg = out['stdout']
        else:
            msg = out['stderr']
        raise CommandExecutionError(
            'firewall-cmd failed: {0}'.format(msg)
        )
    return out['stdout']