Nti.transactions

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

- Fix compatibility with perfmetrics 3.0: drop ``from __future__
import unicode_literals``.

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

- Use the new public ``isRetryableError`` in transaction 2.2. The
interface for this package is unchanged, but a major version bump of
a dependency necessitates a major bump here. See `issue 12
<https://github.com/NextThought/nti.transactions/issues/12>`_.

- Test support for Python 3.7; remove test support for Python 3.4.

- ``TransactionLoop`` is more careful to not keep traceback objects
around, especially on Python 2.

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

- When the ``TransactionLoop`` raises a ``CommitFailedError`` from a
``TypeError``, it preserves the original message.

- Test support for Python 3.6.

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

- Add a new ObjectDataManager that will attempt to execute after
other ObjectDataManagers.

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

- Add support for Python 3.
- Eliminate ZODB dependency. Instead of raising a
``ZODB.POSException.StorageError`` for unexpected ``TypeErrors``
during commit, the new class
``nti.transactions.interfaces.CommitFailedError`` is raised.
- Introduce a new subclass of ``TransactionError``,
``AbortFailedError`` that is raised when an abort fails due to a
system error.