2.7-rc5: juju run does not return command output

[John George]

There is a regression with 2.7-rc5 where juju run does not return the output of the command it executes on the unit. We noted that the output is presented when the --format yaml option is passed and also if 'juju exec' is called rather than 'juju run'. Please see the demonstrated out put below:

alexb@blackFire:~$ juju run -u fio/leader pwd
/var/lib/juju/agents/unit-fio-0/charm

$ juju run -u fio/leader pwd --format yaml
- Stdout: |
    /var/lib/juju/agents/unit-fio-0/charm
  UnitId: fio/0

alexb@blackFire:~$ juju show-controller
localhost-localhost:
  details:
    uuid: 33a9125b-6c54-436f-838d-3185b48431be
    controller-uuid: 33a9125b-6c54-436f-838d-3185b48431be
    api-endpoints: ['10.80.4.33:17070']
    cloud: localhost
    region: localhost
    agent-version: 2.6.10
    mongo-version: 3.6.3

ubuntu@prodymcprodface-cpe-e3efd0c9-d965-4cdc-a990-6f77a56368c5:~/cpe/foundation$ juju run -m openstack -u vault/leader 'pwd'

ubuntu@prodymcprodface-cpe-e3efd0c9-d965-4cdc-a990-6f77a56368c5:~/cpe/foundation$ juju run --format yaml -m openstack -u vault/leader 'pwd'
- Stdout: |
    /var/lib/juju/agents/unit-vault-0/charm
  UnitId: vault/0

ubuntu@prodymcprodface-cpe-e3efd0c9-d965-4cdc-a990-6f77a56368c5:~/cpe/foundation$ juju show-controller
foundations-maas:
  details:
    uuid: 52dcd6f4-c171-4bca-8bac-48c3ccec2f49
    controller-uuid: 52dcd6f4-c171-4bca-8bac-48c3ccec2f49
    api-endpoints: ['10.246.64.200:17070', '10.246.64.202:17070', '10.246.64.201:17070']
    cloud: maas_cloud
    region: default
    agent-version: 2.7-rc5
    controller-model-version: 2.7-rc5
    mongo-version: 3.6.3

ubuntu@prodymcprodface-cpe-e3efd0c9-d965-4cdc-a990-6f77a56368c5:~/cpe/foundation$ juju exec -m openstack -u vault/leader 'pwd'
/var/lib/juju/agents/unit-vault-0/charm

[Ian Booth (wallyworld)]

There was a typo in the code to support backwards compatibility with juju run vs juju exec

https://github.com/juju/juju/pull/10937