Zope-schema

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- Remove trailing slash in MANIFEST.in, it causes Winbot to crash.

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- Add TreeVocabulary for nested tree-like vocabularies.

- Fix broken Object field validation where the schema contains a Choice with
ICountextSourceBinder source. In this case the vocabulary was not iterable
because the field was not bound and the source binder didn't return the
real vocabulary. Added simple test for IContextSourceBinder validation. But a
test with an Object field with a schema using a Choice with
IContextSourceBinder is still missing.

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- Fix bug in ``fromUnicode`` method of ``DottedName`` which would fail
validation on being given unicode. Introduced in 4.0.0.

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- Fix deprecated unittest methods.

- Port to Python 3. This adds a dependency on six and removes support for
Python 2.5.

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- Fix broken Object field validation. Previous version was using a volatile
property on object field values which ends in a ForbiddenAttribute error
on security proxied objects.

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- Implement a ``defaultFactory`` attribute for all fields. It is a callable
that can be used to compute default values. The simplest case is::

Date(defaultFactory=datetime.date.today)

If the factory needs a context to compute a sensible default value, then it
must provide ``IContextAwareDefaultFactory``, which can be used as follows::

provider(IContextAwareDefaultFactory)
def today(context):
return context.today()

Date(defaultFactory=today)