Nti.site

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

- Improvements and bug fixes to ``nti.testing.print_tree``.

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

- Test changes: Depend on ``nti.testing`` 3.0 and refactor certain
internal test methods for improved isolation. The dependency on
ZODB is now >= 5.6.0.

Some internal, undocumented test attributes (``current_mock_db``, a
ZODB.DB, and ``current_transaction`` which was actually a ZODB
Connection) have been removed. The former is replaced with
``nti.testing.zodb.ZODBLayer.db``, and there is no replacement for
the later.

- Add the module ``nti.site.testing``. This contains extensible,
documnted versions of the functions that were previously in
``nti.site.tests`` as private helpers.

- Add support for Python 3.8.

- Make ``hostpolicy.install_main_application_and_sites()`` set the
*root_alias* correctly. Previously, instead of setting it to the
*root_name*, it set it to the *main_name*.

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

- Update ``run_job_in_site`` to work with nti.transactions 3.0 and
enable the optimizations of an explicit transaction manager.

- Test support for Python 3.7.

- Stop claiming support for Python 3.4 or 3.5; those aren't tested.

- Test support for PyPy3.

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

- Add subscriber to unregister ``IBaseComponents`` on host policy folder
removal.

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

- Allow ``ISiteMapping`` to map between persistent sites.

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

- Add the ability to map one (non-persistent) site to another via
configuration. If ``get_site_for_site_names`` does not find
persistent site components for a site, it will fall back to looking
for a configured ``ISiteMapping`` pointing to another target site.