As the charm is not correctly detecting the neutron version, I suspect its rendering the wrong configuration file for the OpenStack Mitaka release, resulting in your error.
Could you provide the log files for the charm from /var/log/juju/unit-neutron-gateway-0.log please?
As the charm is not correctly detecting the neutron version, I suspect its rendering the wrong configuration file for the OpenStack Mitaka release, resulting in your error.
Could you provide the log files for the charm from /var/log/ juju/unit- neutron- gateway- 0.log please?