/usr/bin/landscape-schema fails with database is not currently accepting connections

[Diko Parvanov]

Running a migration from 19.10, bionic, pgsql 10 to 23.03, pgsql 12, focal trying to run the /usr/bin/landscape-schema script fails with exceptions that all dbs are "not currently accepting connections", as in:

Traceback (most recent call last):
  File "/opt/canonical/landscape/canonical/landscape/scripts/schema.py", line 327, in run
    main_schema.check(main_store)
  File "/usr/lib/python3/dist-packages/storm/schema/schema.py", line 143, in check
    raise UnappliedPatchesError(unapplied_versions)
storm.schema.schema.UnappliedPatchesError: [477, 478, 479, 480, 481, 482, 483]

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/storm/exceptions.py", line 165, in wrap_exceptions
    yield
  File "/usr/lib/python3/dist-packages/storm/database.py", line 187, in wrapper
    return attr(*args, **kwargs)
psycopg2.errors.ObjectNotInPrerequisiteState: database "landscape-resource-1" is not currently accepting connections
CONTEXT: parallel worker

seems that if it's charm installed (and in my case it is), the following code is ran locking all dbs in https://git.launchpad.net/landscape/tree/canonical/landscape/scripts/schema.py?h=23.03#n333

if is_charm_deployment():
    try:
      ensure_no_other_connections(zstorm)

but because there are no connections made to any db prior to that (my testing indicates that with SELECT * FROM pg_stat_activity), this raises an error above and doesn't continue the schema upgrade

[Diko Parvanov (dparv)]

Commenting out the ensure_no_other_connections(zstorm) and adding pass the schema upgrade works just fine.