Per deprecation timeline.

Per deprecation timeline.

When someone needs to build a custom backend-specific GIS lookup, it
is much easier done if getting the spatial operator class happens in
a dedicated method (no need to rewrite the entire as_sql() method).

Without an explicit 'level', only messages at WARNING or higher
are handled. This makes the config consistent with the docs
which say, "The django catch-all logger sends all messages at
the INFO level or higher to the console."

Reverted "Fixes #24727 -- Prevented ClearableFileInput from masking
exceptions on Python 2" and added a regression test.

This reverts commit 5c412dd8.

Most likely this is a losing fight -- people seem to love this small
convention -- but at least the reasons for avoiding it will be
documented.

Refs #25356.

This commits lifts the restriction that the outermost atomic block must
be declared with savepoint=False. This restriction was overly cautious.

The logic that makes it safe not to create savepoints for inner blocks
also applies to the outermost block when autocommit is disabled and a
transaction is already active.

This makes it possible to use the ORM after set_autocommit(False).
Previously it didn't work because ORM write operations are protected
with atomic(savepoint=False).