In "nova-manage cell_v2 create_cell" CLI help, the parameter ie. "transport-url" and "database_connection" are mentioned as optional parameters but they are treated as positional parameters.

[Swati Bansal]

In "nova-manage cell_v2 create_cell" CLI help, the parameter ie. "transport-url" and "database_connection" are mentioned as optional parameters but they are treated as positional parameters.
If the optional parameters ie. "transport-url" and "database_connection" are not provided, the CLI throws an error "The specified transport_url and/or database_connection combination already exists for another cell with uuid 313fe809-ce91-490a-b147-4a74dc0ad071".

<Supplementary Information>
Output of help:
[root@openstackq ~(keystone_admin)]# nova-manage cell_v2 create_cell -h
usage: nova-manage cell_v2 create_cell [-h] [--name <cell_name>]
                                       [--database_connection <database_connection>]
                                       [--transport-url <transport_url>]
                                       [--verbose]

[Matt Riedemann (mriedem)]

The CLI options are optional because if not specified the values are pulled from the config file, which you can provide via the --config-file option, and so you don't have to write URLs with credentials into scripts. The fact it fails with "The specified transport_url and/or database_connection combination already exists for another cell with uuid" is because you're trying to create a cell using the same config as another cell that already exists, so I'm not sure that this is a bug.