The issue was fixed on master in e9103402
so this just forwardports the test and release notes from stable/1.7.x.

Forwardport of 2d12a599 from stable/1.7.x

Custom form fields having a `queryset` attribute but no
`limit_choices_to` could no longer be used in ModelForms.

Refs #2445.

Thanks to artscoop for the report.

__init__ isn't allowed to return anything other than None and it isn't
common practice to include a return statement.

Thanks Baptiste Mispelon for review.

Usage of this method was removed pre 1.0 (c2ba59fc).

This fix is necessary for Python 3.5 compatibility (refs #23763).

Thanks Berker Peksag for review.

Made _do_update behave more strictly according to its docs,
including a corner case when specific concurent updates are
executed and select_on_save is set.

`io.open` is required on Python 2.7. Just `open` would work on Python 3.

JavaScript string extraction support has been added in gettext
0.18.3.
Thanks Aymeric Augustin for the review.

Added a test for the condition safe_join is designed to prevent.

Previously, a generic ValueError was raised. It was impossible to tell
an intentional exception raised to implement safe_join's contract from
an unintentional exception caused by incorrect inputs or unexpected
conditions. That resulted in bizarre exception catching patterns, which
this patch removes.

Since safe_join is a private API and since the change is unlikely to
create security issues for users who use it anyway -- at worst, an
uncaught SuspiciousFileOperation exception will bubble up -- it isn't
documented.

Removed legacy code from old transaction system

Query the table introduced in MySQL 5.1; refs #23144.

Thanks to w0rp for the report

This snippet wasn't particularly helpful as `add_error()` is described
in greater details in the following section.

Thanks Claude Paroz for the report.

Thanks vanschelven and expleo for the initial patch.