feat(setup.py): increase cubicweb max version to 3.31.x

1 job for !15 with topic/default/set_cubes_cw_max_version in 29 seconds (queued for 3 seconds)
latest detached
Status Job ID Name Coverage
  Tests
failed py27 #384541

00:00:29

 
Name Stage Failure
failed
py27 Tests
WARNING: You are using pip version 20.0.2; however, version 20.3.4 is available.
You should consider upgrading via the '/builds/cubicweb/cubes/email/.tox/py27/bin/python -m pip install --upgrade pip' command.

=================================== log end ====================================
ERROR: could not install deps [-rrequirements-test.txt]; v = InvocationError(u'/builds/cubicweb/cubes/email/.tox/py27/bin/python -m pip install -rrequirements-test.txt', 1)
___________________________________ summary ____________________________________
ERROR: py27: could not install deps [-rrequirements-test.txt]; v = InvocationError(u'/builds/cubicweb/cubes/email/.tox/py27/bin/python -m pip install -rrequirements-test.txt', 1)
Cleaning up file based variables
ERROR: Job failed: command terminated with exit code 1