What's the problem this feature will solve?

Having a nicely formatted assert when comparing mappings that are not subclass of dicts.

Describe the solution you'd like

I think it's enough to change the check in _compare_eq_any and similar that at the moment does isinstance(x, dict) to mapping, since it seems that _compare_eq_dict already supports mappings.

Alternative Solutions

At the moment, I just do assert dict(d1) == dict(d2)

Additional context