[BUG] Migration does not run locally after upgrading to 1.19.1

[prabhumarappan]

Describe the bug
After upgrading to 1.19.1, we are having issues with running migration locally (on a single instance MongoDB, running on docker).

To Reproduce

Expected behavior
When running locally or without a replica set, this should't run transactions and run into this error.

Additional context
Add any other context about the problem here.

[prabhumarappan]

@roman-right we can probably check if client.is_mongos is True here, then run it in session. Otherwise, we can just pass the session as None and make it Optional here

[roman-right]

Hi! Hm, this makes sense. The problem is using migrations without transactions is a bit risky as it will not roll back correctly. I probably can add something like --dev flag for the client to run it without transactions if it can not run them

[prabhumarappan]

@roman-right, that works, thanks!

[mikeler216]

Hey is there somebody working on this if not I can try to pick this up?