This change https://review.openstack.org/#/c/515034/ (added in queens)
makes the archive_deleted_rows CLI remove instance mappings and request
specs from the API database if there are instances archived from the
main nova/cell database. However for this to work, the api database
connection should be set in the config file. So in the case that the
API database is not configured in the config file being used to run the
CLI, we should gracefully handle the condition and and stop archiving thus
prompting the user to set the api_db config and try the archival operation
again. This patch fixes the graceful handling.
Change-Id: I0c7b802a453aa423c7273ab724ce78eac0cfed4c
Closes-Bug: #1753833
8da6831e63