Error messages improvements : remove the brackets for the details in Failure

[smarie]

This validation message is received when checking that '' is non empty

ValidationError[ValueError]: Error validating [f='']. Validation function [non_empty] raised Empty: len(x) > 0 does not hold for x=. Wrong value: [].

It raises the question of "what to display in the message ?" Indeed displaying [] in the end of the message is not satisfying to me. Maybe we should use repr(x) without brackets rather.