Sample failure in gate:


May 06 00:50:16.378720 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]: 2019-05-06 00:50:16.377 7630 ERROR kuryr_libnetwork.utils [-] Unexpected error happened: Deleting the veth pair failed.: VethDeletionFailure: Deleting the veth pair failed.
May 06 00:50:16.378720 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]: Traceback (most recent call last):
May 06 00:50:16.379043 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]:   File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1813, in full_dispatch_request
May 06 00:50:16.381128 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]:     rv = self.dispatch_request()
May 06 00:50:16.381128 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]:   File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1799, in dispatch_request
May 06 00:50:16.381128 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]:     return self.view_functions[rule.endpoint](**req.view_args)
May 06 00:50:16.381600 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]:   File "/opt/stack/kuryr-libnetwork/kuryr_libnetwork/controllers.py", line 1291, in network_driver_delete_endpoint
May 06 00:50:16.382960 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]:     LOG.error('Cleaning the veth pair up was failed.')
May 06 00:50:16.382960 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]:   File "/usr/local/lib/python2.7/dist-packages/oslo_utils/excutils.py", line 220, in __exit__
May 06 00:50:16.383588 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]:     self.force_reraise()
May 06 00:50:16.383588 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]:   File "/usr/local/lib/python2.7/dist-packages/oslo_utils/excutils.py", line 196, in force_reraise
May 06 00:50:16.383891 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]:     six.reraise(self.type_, self.value, self.tb)
May 06 00:50:16.383891 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]:   File "/opt/stack/kuryr-libnetwork/kuryr_libnetwork/controllers.py", line 1281, in network_driver_delete_endpoint
May 06 00:50:16.383891 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]:     endpoint_id, neutron_port)
May 06 00:50:16.383891 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]:   File "/opt/stack/kuryr-libnetwork/kuryr_libnetwork/port_driver/drivers/veth.py", line 81, in delete_host_iface
May 06 00:50:16.384451 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]:     return binding.port_unbind(endpoint_id, neutron_port)
May 06 00:50:16.384451 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]:   File "/usr/local/lib/python2.7/dist-packages/kuryr/lib/binding/__init__.py", line 75, in port_unbind
May 06 00:50:16.384762 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]:     return driver.port_unbind(endpoint_id, neutron_port, **kwargs)
May 06 00:50:16.384762 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]:   File "/usr/local/lib/python2.7/dist-packages/kuryr/lib/binding/drivers/veth.py", line 123, in port_unbind
May 06 00:50:16.384762 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]:     'Deleting the veth pair failed.')
May 06 00:50:16.384762 ubuntu-bionic-rax-ord-0005988061 kuryr-server[7630]: VethDeletionFailure: Deleting the veth pair failed.