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.

Thanks NotSqrt for the report; refs #23741.

Thanks to `django-hstore` for inspiration in some areas, and many people
for reviews.

Thanks elvard and gkmngrgn for work on the patch and Markus H. for review.

Fixed #23300 -- Made assertTemplateUsed throw an error on responses not fetched using the test client.

Thanks zags for the report and bmispelon for the patch.

Added getvalue() to HttpResponse to return the content of the response,
along with a few other methods to partially match io.IOBase.

Thanks Claude Paroz for the suggestion and Nick Sanford for review.