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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 system_requirements():
 """ Check if all necessary packages are installed on system :return: None or raise exception if some tooling is missing """

        command_exists("systemd-nspawn",
            ["systemd-nspawn", "--version"],
            "Command systemd-nspawn does not seems to be present on your system"
            "Do you have system with systemd")
        command_exists(
            "machinectl",
            ["machinectl", "--no-pager", "--help"],
            "Command machinectl does not seems to be present on your system"
            "Do you have system with systemd")
        if "Enforcing" in run_cmd(["getenforce"], return_output=True, ignore_status=True):
            logger.error("Please disable selinux (setenforce 0), selinux blocks some nspawn operations"
                         "This may lead to strange behaviour")