[server/session] add missing rollback when freeing a db connection
When we let go of a cnxset and give it back to the pool, we need to make
sure it's not in the middle of a transaction.
We got bitten by a migration where the connection used by admin's
repo.connect was not rolled back before attempting the migration,
causing a deadlock because it had a lock on a table. This could
potentially also be an issue for e.g. hooks or looping tasks that didn't
explicitly rollback before calling free_cnxset or moving out of a
ensure_cnx_set block.
What's new in CubicWeb 3.17?
============================
New functionalities
--------------------
* add a command to compare db schema and file system schema
(see `#464991 <http://www.cubicweb.org/464991>`_)
* Add CubicWebRequestBase.content with the content of the HTTP request (see #2742453)
(see `#2742453 <http://www.cubicweb.org/2742453>`_)
* Add directive bookmark to ReST rendering
(see `#2545595 <http://www.cubicweb.org/ticket/2545595>`_)
* Allow user defined final type
(see `#124342 <https://www.logilab.org/ticket/124342>`_)
API changes
-----------
* drop typed_eid() in favour of int() (see `#2742462 <http://www.cubicweb.org/2742462>`_)
* The SIOC views and adapters have been removed from CubicWeb and moved to the
`sioc` cube.
* The web page embedding views and adapters have been removed from CubicWeb and
moved to the `embed` cube.
* The email sending views and controllers have been removed from CubicWeb and
moved to the `massmailing` cube.
* ``RenderAndSendNotificationView`` is deprecated in favor of
``ActualNotificationOp`` the new operation use the more efficient *data*
idiom.
* Looping task can now have a interval <= ``0``. Negative interval disable the
looping task entirely.
* We now serve html instead of xhtml.
(see `#2065651 <http://www.cubicweb.org/ticket/2065651>`_)
Deprecation
---------------------
* ``ldapuser`` have been deprecated. It'll be fully dropped in the next
version. If you are still using ldapuser switch to ``ldapfeed`` **NOW**!
* ``hijack_user`` have been deprecated. It will be dropped soon.
Deprecated Code Drops
----------------------
* The progress views and adapters have been removed from CubicWeb. These
classes were deprecated since 3.14.0. They are still available in the
`iprogress` cube.
* API deprecated since 3.7 have been dropped.