$juju status quantum-gateway
...
services:
  quantum-gateway:
    charm: local:trusty/quantum-gateway-64
    exposed: false
    relations:
      cluster:
      - quantum-gateway
    units:
      quantum-gateway/0:
        agent-state: error
        agent-state-info: 'hook failed: "config-changed"'
        agent-version: 1.18.4.1
        machine: 1/lxc/4
        public-address: 10.0.3.52
      quantum-gateway/1:
        agent-state: error
        agent-state-info: 'hook failed: "config-changed"'
        agent-version: 1.18.4.1
        machine: 2/lxc/4
        public-address: 10.0.3.153

$ juju resolved --retry quantum-gateway/1
ERROR cannot set resolved mode for unit "quantum-gateway/1": already resolved