prep for migration failed flag

Implemented with minimal changes

UTF-8 should be a consistent default for opening files in text mode.

This change is motivated by wanting to log sim mode job "submissions"

main function takes in `argv` as an optional argument and uses `sys.argv` if it is missing. This allows for easier testing.

It needs to be a tuple even when there's a single argument.

https://in.xfel.eu/redmine/issues/87389