get_language() can return None when translations are deactivated.
Thanks Nicola Peduzzi for the reporti and Tim Graham for the review.

Thanks Domas Lapinskas for the report and Tim Graham for the
review.

Thanks to gfairchild for the report and Claude for the review.

Thanks to knbk for the report.

Forwardport of e7366ab1 from stable/1.8.x

Fixes a regression introduced in 53c2cf1e.

Forward port of 5483c66f from stable/1.8.x

Forward port of d1b206da from stable/1.8.x

Forward port of 05a781a4 from stable/1.8.x

This change:

* Makes the InclusionNode cache-safe by removing render-time side effects
  to its nodelist.
* Ensures the render_context stack is properly scoped and reset by updating
  the render call to use Template.render rather than Nodelist.render.

Rendering a Jinja template with self in the context threw an error.
While self is a reserved variable in Jinja, including self in the
context is not an error, so Django should respect that.

Thanks Claude Paroz and Tim Graham for the review

Calling Migration.mutate_state() now also allows to do in_place
mutations in case an intermediate state is thrown away later.

Thanks Anssi Kääriäinen for the idea, Ryan Hall for parts of the patch,
and Claude Paroz and Tim Graham for the review

SimpleCookie.__repr__() changed in
https://hg.python.org/cpython/rev/88e1151e8e02

Thanks Aymeric Augustin and Florian Apolloner for work on the patch.

Thanks Florian Apolloner for the review.

Thanks simon29 for report, and freakboy3742, floledermann,
jacob, claudep and collinanderson for discussing the task.

Thanks Tim Graham for the review.