logilab-common #294478 testlib.TestCase.datadir fails when cls.__module__ is qualified [validation pending]

we use __import__ wrongly.

prioritynormal
typebug
done in1.0.0
load0.500
load left0.000
closed by#ac30dd4ee478 [testlib] Fix datadir property (closes #294478)
patch[testlib] Fix datadir property (closes #294478) [applied]