The offending line is: 678 out = subprocess.check_output(['resolvectl', 'query', 'math.lab']) With -1006: $ sudo pdb3 ./networkd-test.py > /home/ubuntu/systemd-249.11/test/networkd-test.py(21)() -> import errno (Pdb) b 678 Breakpoint 1 at /home/ubuntu/systemd-249.11/test/networkd-test.py:678 (Pdb) c systemd-network:x:100:102:systemd Network Management,,,:/run/systemd:/usr/sbin/nologin test_bridge_init (__main__.BridgeTest) ... ok test_bridge_port_priority (__main__.BridgeTest) ... ok test_bridge_port_priority_set_zero (__main__.BridgeTest) It should be possible to set the bridge port priority to 0 ... ok test_bridge_port_property (__main__.BridgeTest) Test the "[Bridge]" section keys ... ok test_coldplug_dhcp_ip4_only (__main__.DnsmasqClientTest) ... ok test_coldplug_dhcp_ip4_only_no_ra (__main__.DnsmasqClientTest) ... ok test_coldplug_dhcp_ip6 (__main__.DnsmasqClientTest) ... ok test_coldplug_dhcp_yes_ip4 (__main__.DnsmasqClientTest) ... ok test_coldplug_dhcp_yes_ip4_no_ra (__main__.DnsmasqClientTest) ... ok test_hotplug_dhcp_ip4 (__main__.DnsmasqClientTest) ... ok test_hotplug_dhcp_ip6 (__main__.DnsmasqClientTest) ... ok test_resolved_domain_restricted_dns (__main__.DnsmasqClientTest) resolved: domain-restricted DNS servers ... > /home/ubuntu/systemd-249.11/test/networkd-test.py(678)test_resolved_domain_restricted_dns() -> out = subprocess.check_output(['resolvectl', 'query', 'math.lab']) (Pdb) (in another terminal) ubuntu@curly:~$ resolvectl query math.lab math.lab: 10.241.3.3 -- link: testvpnrouter -- Information acquired via protocol DNS in 10.4732s. -- Data is authenticated: no; Data was acquired via local or encrypted transport: no -- Data from: network With -1007 $ sudo pdb3 ./networkd-test.py > /home/ubuntu/systemd-249.11/test/networkd-test.py(21)() -> import errno (Pdb) b 678 Breakpoint 1 at /home/ubuntu/systemd-249.11/test/networkd-test.py:678 (Pdb) c systemd-network:x:100:102:systemd Network Management,,,:/run/systemd:/usr/sbin/nologin test_bridge_init (__main__.BridgeTest) ... ok test_bridge_port_priority (__main__.BridgeTest) ... ok test_bridge_port_priority_set_zero (__main__.BridgeTest) It should be possible to set the bridge port priority to 0 ... ok test_bridge_port_property (__main__.BridgeTest) Test the "[Bridge]" section keys ... ok test_coldplug_dhcp_ip4_only (__main__.DnsmasqClientTest) ... ok test_coldplug_dhcp_ip4_only_no_ra (__main__.DnsmasqClientTest) ... ok test_coldplug_dhcp_ip6 (__main__.DnsmasqClientTest) ... ok test_coldplug_dhcp_yes_ip4 (__main__.DnsmasqClientTest) ... ok test_coldplug_dhcp_yes_ip4_no_ra (__main__.DnsmasqClientTest) ... ok test_hotplug_dhcp_ip4 (__main__.DnsmasqClientTest) ... ok test_hotplug_dhcp_ip6 (__main__.DnsmasqClientTest) ... ok test_resolved_domain_restricted_dns (__main__.DnsmasqClientTest) resolved: domain-restricted DNS servers ... > /home/ubuntu/systemd-249.11/test/networkd-test.py(678)test_resolved_domain_restricted_dns() -> out = subprocess.check_output(['resolvectl', 'query', 'math.lab']) (Pdb) (in another terminal) ubuntu@curly:~$ resolvectl query math.lab math.lab: resolve call failed: Lookup failed due to system error: No route to host