Implement handling of Expected exceptions in Doctests.

[Carreau]

Currently we just exclude docstrings examples which raise exceptions unconditionally.

We should check that the error match what is in the docstring, like the classic doctes.

[asmeurer]

If papyri is going to execute doctest examples it should just use the doctest module directly.

[Carreau]

The problem is that we execute also for Jedi to properly infer which objects are in example.
It's not present right now, but we used to have cross links for every token in code example.
We also use that to capture the created images by matplotlib, and display them

I was unable to do it with doctest.

[asmeurer]

In my experience doctest is pretty extensible. I think it might be possible to hook into it to handle these things.

[melissawm]

May be of interest: https://github.com/ev-br/scpdt

[asmeurer]

Really we need to make the whole doctester pluggable, so that different libraries can use different doctesting tools. Picking just one thing as a default is in appropriate for all libraries, although if there has to be a default, it should be the basic doctest.

[Carreau]

I agree that we should make it pluggable, like many other things, but this might come at a later date, once we have a better understanding of what the needs are.