cubicweb #4881300 [web/data] Never hide JS errors in our Deferred implementation [validation pending]

[web/data] Never hide JS errors in our Deferred implementation

Modern browsers have good debugging tools, let exceptions go all the way up.

prioritynormal
typebug
done in3.20.3
load1.000
load left0.000
closed by#7f1f7f710b16 [web/data] Never hide JS errors in our Deferred implementation
patch[web/data] Never hide JS errors in our Deferred implementation [applied]