We'd been using `skip` because when we started with mypy next to nothing
passed it, and checking one file would spew errors with other files and it
just wasn't conducive to making at least *some* progress.
But now we should have every single file passing, so this is the right thing
to do.
`mypy EDMarketConnector.py` was throwing a warning:
By default the bodies of untyped functions are not checked, consider using --check-untyped-defs [annotation-unchecked]
for some things. Bizarrely including e.g.
play_bad: bool = False
