cubicweb #344878 Custom validation error messages [open]

Being able to customize validation error messages would be cool. It is relatively easy to catch the ValidationError exception for a given attribute and customize it, but we can not go deeper easily : accessing the validation type itself would be nice. Another way to customize user messages would be client-side. Using e.g. jquery.validate it is possible to generate a client-side validator based on the schema constraints (not all constraints could be supported, notably rql-based ones or only with ajax requests which is difficult to set up and not that useful to end-user). I wrote a very simple code with that kind of thing in mind, it could be useful just to start with (see syt : bsport/views/mixins.py from SecondWeb), but must be considerably improved to reach cw code quality standards and generality ;-)