Instances are created but unable to receive IP address over dhcp due to the fact that kernel lacks of namespace support

Issue

Instances are created correctly but IP is not assigned over DHCP due to the fact that kernel doesn't support namespaces:
in /var/log/quantum/dhcp-agent.log

ERROR [quantum.agent.dhcp_agent] Unable to enable dhcp.
RuntimeError:
Command: ['sudo', 'quantum-rootwrap', '/etc/quantum/rootwrap.conf', 'ip', 'netns', 'add', 'qdhcp-263c7f35-d52e-4f02-2358-7f2ccdb1fbd7']
Exit code: 255
Stdout: ''
Stderr: 'Bind /proc/self/ns/net -> /var/run/netns/qdhcp-263c7f35-d52e-4f02-2358-7f2ccdb1fbd7 failed: No such file or directory\n'

And also:

ls -al /proc/self/ns/net
ls: cannot access /proc/self/ns/net: No such file or directory