Python 2.6 shows no error messages

[catriuspham]

For example, we have this expectation:

expect(1).to.eq(2)

In Python 3, we get this error message:

robber.bad_expectation.BadExpectation: Expected int("1") to equal int("2")

But in Python 2.6, we only get this:

BadExpectation

[hieueastagile]

It could be how the base exception was string-ify, I think we can override this via __str__ or __repr__ somehow, not really an issue then.

[tklarryonline]

Since __str__ is overridden already, I think we could add __repr__ as well.