def test_cgroupsSuggestsRealSystem(self):
        """
        If the platform is Linux, and the cgroups file (faked out here) exists,
        and none of the paths starts with C{/docker/}, C{isDocker()} returns
        C{False}.
        """
        cgroupsFile = self.mktemp()
        with open(cgroupsFile, 'wb') as f:
            # real cgroups file from a Fedora 17 system
            f.write(b"""9:perf_event:/
8:blkio:/
7:net_cls:/
6:freezer:/
5:devices:/
4:memory:/
3:cpuacct,cpu:/
2:cpuset:/
1:name=systemd:/system""")

        platform = Platform(None, 'linux')
        self.assertFalse(platform.isDocker(_initCGroupLocation=cgroupsFile))

        If the platform is Linux, and the cgroups file (faked out here) exists,
        and none of the paths starts with C{/docker/}, C{isDocker()} returns
        C{False}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/test/test_runtime.py