cubicweb-tracker #3790324 broken __json_encode__ for project and version [validation pending]

both the methods and their tests are b0rked

priorityimportant
typebug
done in1.15.3
load0.500
load left0.000
closed by#045bedcf9998 [entities] fix commit #7c6b6120f381 which breaks __json_encode__
patch[entities] fix commit #7c6b6120f381 which breaks __json_encode__ [applied]