logilab-common #99627 Make testlib module compatible with other python flavours [validation pending]

Testlib module currently use __builtins__, this is considered to be an implementation detail, and it's generally recommended to only use the 'builtins' object.

done in0.58.1
load left0.000
closed by#121719962a24 Adapt testlib.py in order to be compatible with Jython which doesn't have a __builtins__ module. Closes #99627.