Provide NameError/AttributeError suggestions in traceback.py

[ambv]

Python 3.10 added NameError and AttributeError suggestions in raised exceptions, in the form of:

>>> dim
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'dim' is not defined. Did you mean: 'dir'?

This is implemented in Python/suggestions.c and unavailable in the pure Python implementation of traceback formatting in Lib/traceback.py. This makes the output of both different, which is problematic for tooling using traceback.py, as well as for alternative implementations of Python like PyPy and GraalPy.

Let's implement the equivalent of suggestions.c in Lib/traceback.py to bring both in line.

[ambv]

cc @cfbolz

[sweeneyde]

I'm not sure if exact equivalence with suggestions.c is required, but if not, IIRC there was at one point a call to use difflib's get_close_matches(), which might simplify things.

[cfbolz]

@sweeneyde the plan is to start from PyPy's implementation, @ambv and I started working on that today (it's a port of Pablo's original commit, at the time I didn't your later changes hadn't landed).

[gpshead]

cc @Yhg1s

[ambv]

Fixed!

[cfbolz]

wonderful, thank you @ambv, @pablogsal and @sweeneyde 😊