Description of problem:
During the upgrade the beta repos were set and the environment variable "FOREMAN_MAINTAIN_USE_BETA='1'" was not used. To work around this the whitelist option of 'repositories-validate' was used.

After the pulp3 migration completed the installer runs again to upgrade with pulp3 settings. Once the installer reaches the point of:
Re-running the installer to switch specified content over to pulp3    [OK]
--------------------------------------------------------------------------------
Setup repositories: 

the installer fails because the name of this whitelist step is 'repositories-setup'. After adding this step to the whitelist options and running again, the installer fails to run continuously because the content is already migrated but the migration steps from the installer are still being called every time.

Version-Release number of selected component (if applicable):
6.10.0 Snap14

How reproducible:
Every time

Steps to Reproduce:
1. Do not use standard repositories or environment variable "FOREMAN_MAINTAIN_USE_BETA='1'" or figure out another way to cause the installer to fail AFTER the pulp migration
2. Upgrade using installer option '--whitelist="repositories-validate"'
3.

Actual results:
Installer fails continuously because pulp content is already migrated

Expected results:
After the pulp content is upgraded and the installer re-runs to upgrade the Satellite with pulp3 as seen here in this step:
===============================
Starting the following service(s):
pulpcore-api, pulpcore-content, pulpcore-resource-manager, pulpcore-worker@1, pulpcore-worker@2, pulpcore-worker@3, pulpcore-worker@4
/ All services started                                                [OK]      
--------------------------------------------------------------------------------
Switch support for certain content from Pulp 2 to Pulp 3: 
Performing final content migration before switching content
Checking for valid Katello configuraton.
Starting task.
2021-08-22 14:27:36 -0400: Importing migrated content type erratum: 14000/12657            
Content Migration completed successfully
Performing a check to verify everything that is needed has been migrated

Switching specified content over to pulp 3
Checking for valid Katello configuraton.
Content Switchover completed successfully
Re-running the installer to switch specified content over to pulp3    [OK]
===============================
The installer should be able to detect that the pulp migration has completed and is not needed again.

Additional info:
After hitting this, setting the environment variable "FOREMAN_MAINTAIN_USE_BETA='1'" and/or including the whitelist value 'repositories-setup' has no effect on the failing outcome of the upgrade. This suggests that currently, at this point or any other point in the re-run of the upgrade after the migration will indefinitely fail the upgrade.
Whitelisting this step appears to be the only way to continue forward with the upgrade which results in the failure of the pulp3 migration and hammer ping being the next failure step in the upgrade:
# hammer ping
database:         
    Status:          ok
    Server Response: Duration: 0ms
candlepin:        
    Status:          ok
    Server Response: Duration: 38ms
candlepin_events: 
    Status:          ok
    message:         0 Processed, 0 Failed
    Server Response: Duration: 0ms
candlepin_auth:   
    Status:          ok
    Server Response: Duration: 35ms
katello_events:   
    Status:          ok
    message:         0 Processed, 0 Failed
    Server Response: Duration: 0ms
pulp:             
    Status:          ok
    Server Response: Duration: 100ms
pulp_auth:        
    Status:          ok
    Server Response: Duration: 43ms
pulp3:            
    Status:          FAIL
    Server Response: Message: 503 Service Unavailable
foreman_tasks:    
    Status:          ok
    Server Response: Duration: 3ms