From time to time the nighly ISO integration tests fail. The error is always located around `PermissionError: [Errno 1] failed to run command: None systemctl stop dhcp6c@pppoe20.service` sometimes for pppoe or sometimes ethernet interfaces.
```
DEBUG - ======================================================================
DEBUG - ERROR: test_pppoe_authentication (__main__.PPPoEInterfaceTest.test_pppoe_authentication)
DEBUG - ----------------------------------------------------------------------
DEBUG - Traceback (most recent call last):
DEBUG - File "/usr/libexec/vyos/tests/smoke/cli/test_interfaces_pppoe.py", line 133, in tearDown
DEBUG - self.cli_commit()
DEBUG - File "/usr/libexec/vyos/tests/smoke/cli/base_vyostest_shim.py", line 111, in cli_commit
DEBUG - return self._session.commit()
DEBUG - ^^^^^^^^^^^^^^^^^^^^^^
DEBUG - File "/usr/lib/python3/dist-packages/vyos/configsession.py", line 325, in commit
DEBUG - out = self.__run_command([COMMIT])
DEBUG - ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
DEBUG - File "/usr/lib/python3/dist-packages/vyos/configsession.py", line 252, in __run_command
DEBUG - raise ConfigSessionError(output)
DEBUG - vyos.configsession.ConfigSessionError: [ interfaces pppoe pppoe20 ]
DEBUG - Traceback (most recent call last):
DEBUG - File "/usr/libexec/vyos/services/vyos-configd", line 157, in run_script
DEBUG - script.apply(c)
DEBUG - File "/usr/libexec/vyos/conf_mode/interfaces_pppoe.py", line 120, in apply
DEBUG - p.remove()
DEBUG - File "/usr/lib/python3/dist-packages/vyos/ifconfig/pppoe.py", line 71, in remove
DEBUG - super().remove()
DEBUG - File "/usr/lib/python3/dist-packages/vyos/ifconfig/interface.py", line 399, in remove
DEBUG - self.flush_addrs()
DEBUG - File "/usr/lib/python3/dist-packages/vyos/ifconfig/interface.py", line 1380, in flush_addrs
DEBUG - self.set_dhcpv6(False)
DEBUG - File "/usr/lib/python3/dist-packages/vyos/ifconfig/interface.py", line 1618, in set_dhcpv6
DEBUG - self._cmd(f'systemctl stop {systemd_service}')
DEBUG - File "/usr/lib/python3/dist-packages/vyos/ifconfig/control.py", line 66, in _cmd
DEBUG - return cmd(command, self.debug, env=env)
DEBUG - ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
DEBUG - File "/usr/lib/python3/dist-packages/vyos/utils/process.py", line 209, in cmd
DEBUG - raise OSError(code, feedback)
DEBUG - PermissionError: [Errno 1] failed to run command: None systemctl stop dhcp6c@pppoe20.service
DEBUG - returned:
DEBUG - exit code: 1
DEBUG -
DEBUG - delete [ interfaces pppoe pppoe20 ] failed
```
Most likely issue:
`PermissionError: [Errno 1]` is misleading: `cmd()` raises `OSError(exit_code, feedback);` exit code 1 maps to `PermissionError` in Python 3, so logs point at „permissions“ while the real signal is `systemctl stop` returned 1 (job failure, timeout, restart contention with `Restart=always` on `src/systemd/dhcp6c@.service`