Support Test::Deep expectations

[happy-barney]

Test::Deep provides nice support for writing complex expectations
that comes handy especially when system under test throws objects

    throws_ok
        { code that should throw exception }
        all (
            obj_isa ('Expected::Exception::Instance'),
            methods (
                errcode => 400,
                errstr  => re (qr/foo/),
            )
        ),
        'description'
        ;

Test::Deep is not dependency of Test::Exception, it is only recognized
and used then assuming library is already loaded.

[exodist]

I do not think this should be part of Test::Exception. Test::Exception at this point is fairly legacy, changing it has the potential to effect a lot of things in unintentional ways. Further there are other libraries like Test::Fatal and the equivelent in Test2::Suite, and a couple others which are recommended over Test::Exception.

Test::Exception has to do a few ugly things that the other libraries avoid by a significantly better interface design.

Adding Test::Deep as a testing/development dependency almost certainly creates a dependency cycle.

Also, even Test::Deep has alternatives these days (I wrote one of them), it is not practical to make every legacy library like Test::Exception support all of them.

I am not going to close this outright, if other Test::Exception contributors/maintainers support this change in full or part I am open to listening to people who disagree with me, and do not intend to fight this with any vigor, but I do not think it is a necessary change for such an old library.