Astroid 2.7 breaking change

[martin-traverse]

Astroid just released version 2.7 which deprecates the node_classes namespace. It seems there are maybe other changes too, I am finding Sphinx won'r tun with astroid 2.7. Downgrading to the last 2.6.x fixes the issue. Error output is below.

This could perhaps count as a regression in astroid since node_classes is supposed to remain available and deprecated until 3.0.0, but, since the plan is to remove it anyway, does it makes sense to put a fix in autoapi to use the new 'nodes' namespace instead?

% make html
Running Sphinx v4.1.2
[AutoAPI] Reading files... [ 4%] /Volumes/Data/Dev/Code/trac/trac-runtime/python/src/trac/rt/exceptions.py
Extension error (autoapi.extension):
Handler <function run_autoapi at 0x7f9e0a29c0d0> for event 'builder-inited' threw an exception (exception: module 'astroid.node_classes' has no attribute 'LookupMixIn')
make: *** [html] Error 2

[Pierre-Sassoulas]

Hey sorry for the involuntary breaking change here. We're going to release 2.7.1 fast thanks to @AWhetter but you should also be able to change the import to astroid.nodes