Incrementally adopt f-string support after Stretch is unsupported
The following discussion from !321 (merged) should be addressed:
How about using "new" string formatting? https://docs.python.org/3/library/stdtypes.html?highlight=sprintf#printf-style-string-formatting
This needs Python3.6 which is not available in Stretch.
- Buster gets released
- LAVA adopts
bullseyesuite in CI
- Users migrate to Buster for production systems
- Stretch approaches end of support
- Options which require Python3.6 can be implemented.