The main difficulty in supporting `assert` to behave like `unittest.require` is how to avoid cyclic dependencies. assert is used in low-level modules, but implementing it to dump variables on failure would require either importing std/macros (causing cyclic deps) or using a few select magics from std/macros to implement this.
A 2nd tricky part is avoiding multiple evaluation in some edge cases, eg: `assert lhs() == rhs()` => to avoid multiple evaluation you need: let a = lhs(); let b = rhs(); ... but that can cause un-necessary copies depending on typeof(a); and using `let a = lhs().unsafeAddr` doesn't always work. But unittest.require faces the same problem. Definitely doable and worth doing though.
