[BUG] python-box 7.3.1 breaks netlab

[ipspace]

python-box release 7.3.1 completely breaks netlab, probably due to the change in how they handle "default box" parameter.

The root cause is probably a too-aggressive get somewhere in netlab code, but that might take a bit of time to figure out, so I pinned the python-box version required by netlab to less than 7.3.1 in af7ea2a.

[ipspace]

It looks like cdgriffith/Box#289 fixed the problem (thanks a million to @cdgriffith and @seb5g). Have to run a few more tests, but the CI tests pass with version 7.3.2 :)