Documentation
mypy prints this warning:
Warning: --strict-concatenate is deprecated; use --extra-checks instead
I'm not passing --strict-concatenate on the command line, but I instead have a setup.cfg with strict_concatenate = True. So naturally, I would expect that the strict_concatenate config has been replaced with an extra_checks config, but the docs page The mypy configuration file does not mention such an option but also does not mention that strict_concatenate has been deprecated.
So, either the docs of config options needs to be updated, or the warning is wrong and should only be triggered when --strict-concatenate is passed on the command line.