zope.schema.Object._validate: missing field information in error reports

[Dieter Maurer]

Error reports from ``zope.schema.Object._validate`` for field related errors often lack the information about the affected field. This makes identification of the affected fields unnecessarily difficult.

``dm.zope.schema.schema.Object._validate`` provides a potential fix. It collects pairs fieldname, exception instead of exception alone in the "WrongContainedType" exception.

[Tres Seaver (tseaver)]

Now tracked on Github:

 https://github.com/zopefoundation/zope.schema/issues/16