_populate() sets the populating attribute to prevent infinite recursion in
case a urlconf includes itself. The flag is a threadlocal to avoid a race
condition [1] where one thread sets the flag and another checks it, then
proceeds to access data that's supposed to be populated (e.g. _reverse_dict)
but isn't yet.

The potential still exists for a thread to set the threadlocal, then be
interrupted by a signal such as SIGALRM and raise before resetting the
threadlocal flag. In this scenario, subsequent calls to _populate() in the
same thread will short-circuit erroneously.

The bulk of the method was already wrapped in a try/finally in df41b5a0, but
since a signal interrupt can occur at any line executed by the interpreter,
this moves up the try to ensure threadlocal gets reset.

[1]: https://groups.google.com/d/msg/django-developers/D_bIeinKHjE/4NmVQUJqAgAJ

Thanks Adam Johnson, Carl Meyer, Anssi Kääriäinen, Mariusz Felisiak,
Michael Manfre, and Tim Graham for discussion and review.

Thanks Aymeric Augustin for shepherding the DEP and patch review.
Thanks Marten Kenbeek and Tim Graham for contributing to the code.
Thanks Tom Christie, Shai Berger, and Tim Graham for the docs.

Regression in eef95ea9.

Unneeded since its introduction in 4f138fe5.

Fixed #28597 -- Fixed crash with the name of a model's autogenerated primary key in an Index's fields.

Thanks Florian Apolloner and Tim Graham for review and
contributing to the patch.

From https://github.com/select2/select2/releases/tag/4.0.3

Thanks Tim Graham for the review.

Thanks Josh Smeaton, Mariusz Felisiak, Sergey Fedoseev, Simon Charettes,
Adam Chainz/Johnson and Tim Graham for comments and reviews and Jamie
Cockburn for initial patch.

This reverts commit 01c6a3e2.
Unfortunately, the YAML serializer is not yet able to cope with time values.

Seems unneeded since its introduction in
f59fd15c.

The old location remains for backwards compatibility. Documentation
will be updated separately along with the rest of the URL routing changes.

Thanks Mariusz Felisiak for the Oracle part and Tim Graham for the
review.

Disabled keep-alive to fix the regression in
e6065c7b.