Program crashes when dhcp4 service is offline

[francoismdj]

During a server reboot, netbox-kea-dhcp crashes with the following trace:

août 22 09:32:08 charade netbox-kea-dhcp[846]: netbox: https://netbox-srv, kea: http://127.0.0.1:8000/
août 22 09:32:08 charade netbox-kea-dhcp[846]: Start full sync
août 22 09:32:08 charade netbox-kea-dhcp[846]: pull running config from DHCP server
août 22 09:32:08 charade netbox-kea-dhcp[846]: Traceback (most recent call last):
août 22 09:32:08 charade netbox-kea-dhcp[846]:   File "/usr/local/bin/netbox-kea-dhcp", line 8, in <module>
août 22 09:32:08 charade netbox-kea-dhcp[846]:     sys.exit(run())
août 22 09:32:08 charade netbox-kea-dhcp[846]:   File "/usr/local/lib/netbox-kea-dhcp/lib/python3.10/site-packages/netboxkea/entry_point.py", line 32, in run
août 22 09:32:08 charade netbox-kea-dhcp[846]:     conn.sync_all()
août 22 09:32:08 charade netbox-kea-dhcp[846]:   File "/usr/local/lib/netbox-kea-dhcp/lib/python3.10/site-packages/netboxkea/connector.py", line 83, in sync_all
août 22 09:32:08 charade netbox-kea-dhcp[846]:     self.kea.pull()
août 22 09:32:08 charade netbox-kea-dhcp[846]:   File "/usr/local/lib/netbox-kea-dhcp/lib/python3.10/site-packages/netboxkea/kea/app.py", line 64, in pull
août 22 09:32:08 charade netbox-kea-dhcp[846]:     self.conf = self.api.get_conf()
août 22 09:32:08 charade netbox-kea-dhcp[846]:   File "/usr/local/lib/netbox-kea-dhcp/lib/python3.10/site-packages/netboxkea/kea/api.py", line 68, in get_conf
août 22 09:32:08 charade netbox-kea-dhcp[846]:     return self._request_kea('config-get')['Dhcp4']
août 22 09:32:08 charade netbox-kea-dhcp[846]:   File "/usr/local/lib/netbox-kea-dhcp/lib/python3.10/site-packages/netboxkea/kea/api.py", line 60, in _request_kea
août 22 09:32:08 charade netbox-kea-dhcp[846]:     raise KeaCmdError(f'command "{command}" returns "{text}"')
août 22 09:32:08 charade netbox-kea-dhcp[846]: netboxkea.kea.exceptions.KeaCmdError: command "config-get" returns "unable to forward command to the dhcp4 service: No such file or directory. The server is likely to be offline"

Expected result: handle errors trowned by Kea API, retry later when dhcp4 service is alive