Comment 130 for bug 1863021

Even with all these patches in, I'm still seeing messages like this with devstack running on focal, see https://review.opendev.org/704831:

Jun 01 16:23:06.645371 ubuntu-focal-rax-dfw-0016894858 neutron-dhcp-agent[76054]: DEBUG neutron.agent.linux.utils [-] Running command: ['env', 'LC_ALL=C', 'PATH=/sbin:/us
r/sbin', 'dnsmasq', '--test', '--dhcp-host=tag:foo'] {{(pid=76054) create_process /opt/stack/neutron/neutron/agent/linux/utils.py:87}}
Jun 01 16:23:06.651565 ubuntu-focal-rax-dfw-0016894858 neutron-dhcp-agent[78057]: Exception ignored in: <function _after_fork at 0x7fc960125d30>
Jun 01 16:23:06.651565 ubuntu-focal-rax-dfw-0016894858 neutron-dhcp-agent[78057]: Traceback (most recent call last):
Jun 01 16:23:06.651565 ubuntu-focal-rax-dfw-0016894858 neutron-dhcp-agent[78057]: File "/usr/lib/python3.8/threading.py", line 1454, in _after_fork
Jun 01 16:23:06.651565 ubuntu-focal-rax-dfw-0016894858 neutron-dhcp-agent[78057]: assert len(_active) == 1
Jun 01 16:23:06.651565 ubuntu-focal-rax-dfw-0016894858 neutron-dhcp-agent[78057]: AssertionError:

This happens for neutron-dhcp-agent, neutron-ovs-agent, nova-compute and cinder-volume, seemingly always on a call of subprocess.Popen.