cubicweb #13385274 Binary object are no more pickleable [validation pending]

since recent py3k related changes, Binary instance are pickleable with python 3 but not python 2.7 (because BytesIO are pickleable with python 3 but not with python 2.7).

prioritynormal
typebug
done in3.22.3
load left0.000
closed by#d0f6fe008ec4 Test and fix "pickleability" of Binary objects
patchTest and fix "pickleability" of Binary objects [applied]