Nti.externalization

==================

- Adapt to a change in zope.container 4.4.0 that exposed unsafe
assumptions that ``providedBy(obj)`` would return the exact same
object with the exact same state on a subsequent call. This was
always a bug in the case of concurrency (e.g., if a different thread
called ``directlyProvides`` on the same object, or adjusted the
``__bases__`` of some interface in the IRO); the zope.container
changes made it possible without concurrency. See
https://github.com/zopefoundation/zope.container/issues/38 and
https://github.com/NextThought/nti.externalization/issues/104.

==================

- Fix a faulty assertion error. See `issue 102
<https://github.com/NextThought/nti.externalization/issues/102>`_.

==================

- Make instances of ``fractions.Fraction`` externalize as a string
such as ``"1/3"``. When received by a schema field that can parse
this format, such as ``zope.schema.Rational`` (or higher on the
numeric tower), this means fractions can be round-tripped.
- Support externalizing ``decimal.Decimal`` objects in the YAML
representation.

==================

- Add compatibility with, and require, zope.interface 5.0.

- Document which tagged values are inherited and which are not.

- Stop inheriting ``_ext_is_marker_interface``.

=====================

- Build with Cython 0.29.14 using '3str' as the language level.

- Add support for Python 3.8.

- Update PyYAML to 5.1 and change the default output style slightly.

- Fix tests with Persistent 4.4.3 and above.

- Support zope.interface 4.7, which lets tagged values on interfaces
be inherited, when using ``<registerAutoPackageIO>`` on a module
that had multiple objects implementing a derived interface. See `issue 97
<https://github.com/NextThought/nti.externalization/issues/97>`_.

=====================

- Support ``IFromBytes`` fields introduced by zope.schema 4.8.0. See
`issue 92
<https://github.com/NextThought/nti.externalization/issues/92>`_.

- Make ``validate_field_value`` (and by extension
``InterfaceObjectIO.update_from_external_object``) call
``fromObject`` defined by any fields for non-byte and non-text data.
Previously, only if the field raised a ``WrongContainedTypeError``
would ``fromObject`` be called.