Insufficient error reporting, more humane validation/error messages needed

I have a Dexterity content type with a table z3cform.datagridfield with a row specification that contains

class ITableRowSchema(form.Schema):

date_from = schema.Date(
    title=_(u'Start date'),
    required=True,
    defaultFactory=default_date
)

...
If you pass an ISO8601 string for date_from then the error is:
ˋˋˋ
Module plone.restapi.deserializer.dxcontent, line 114, in call
BadRequest: [{'field': 'table', 'message': u'Wrong contained type', 'error': WrongContainedType([WrongContainedType([AttributeNotFoundError(), AttributeNotFoundError(), AttributeNotFoundError()], '')], 'table')}]
ˋˋˋ

The error message does not contain the name of the offending field date_from but three times it mentions AttributeNotFoundError().

If you omit the require field date_from then the error is also bit useless:

BadRequest: [{'field': 'table', 'message': u'Wrong contained type', 'error': WrongContainedType([WrongContainedType([AttributeNotFoundError(),
AttributeNotFoundError(), AttributeNotFoundError(), AttributeNotFoundError()], '')], 'table')}]
As a user of the REST api I am interested in more precise error message instead of propagating back "internal" tracebacks/errors.

Start at plone.restapi.deserializer.dxcontent around line 114 and reproduce the table validation failures with an ISO8601 date_from value and with the required field omitted. Trace how the nested WrongContainedType and AttributeNotFoundError values become the REST response. Done means the response identifies the offending date_from field and reports a precise, user-facing validation error instead of the repeated internal errors.