API: make tm.assert_foo_equal kwargs keyword-only for rarely-used keywords

[jbrockmendel]

I expect this would need a deprecation cycle cc @jorisvandenbossche ?

[jorisvandenbossche]

Is there a reason you closed this? (I think this is a good idea)

We should have the infrastructure to deprecate it (I think we did something similar for eg read_html), if we want that

[jbrockmendel]

I tend to prune my own open issues fairly aggressively. I may come back to it sooner or later, but there are much higher priorities.