migrate-ovn-db action not working on Bionic

[Frode Nordahl]

juju run-action neutron-api-plugin-ovn/4 migrate-ovn-db i-really-mean-it=yes --wait
unit-neutron-api-plugin-ovn-4:
  UnitId: neutron-api-plugin-ovn/4
  id: "11102"
  message: __init__() got an unexpected keyword argument 'capture_output'
  results: {}
  status: failed
  timing:
    completed: 2021-06-04 15:04:20 +0000 UTC
    enqueued: 2021-06-04 15:04:19 +0000 UTC
    started: 2021-06-04 15:04:19 +0000 UTC

[Jan van Stekelenburg (jvanstekelenburg)]

Me too. Witnessed on ussuri/stable rev 98.

The workaround for this specific run-action to work is simple:

In /var/lib/juju/agents/unit-neutron-api-plugin-ovn-4/charm/actions/migrate-ovn-db
replace "capture_output=True," on L182 with "stdout=subprocess.PIPE, stderr=subprocess.PIPE,"

The capture_output parameter is new in Python version 3.7, and we're on 3.6.