[tox] Update CubicWeb version targets
* In -release, no need to specify cubicweb dependency, its pulled by setup.py.
* Use 3.22 as -compat.
* Point to "default" branch for -dev.
Also remove test directory from posargs.
Philippe Pepiot <philippe.pepiot@logilab.fr> [Thu, 16 Jun 2016 16:25:32 +0200] rev 11623
wsgi: clearer exception when CW_INSTANCE is missing
instance_name is mandatory for cwcfg.config_for()
Raise with a KeyError: 'CW_INSTANCE' instead of hard to read exception.