logilab-common #190806 testlib doesn't handle skip in setUp or tearDown [validation pending]

standard unittest handles them gracefully, lgc's TestCase class turns them into errors.

prioritynormal
typebug
done in0.60.1
load0.200
load left0.000
closed by#e0434df41a2e [testlib] handle skips in setUp and tearDown
patch[testlib] handle skips in setUp and tearDown [applied]